cooling off that c4 corvette



cooling off that c4 corvette

Postby grumpyvette » November 21st, 2010, 10:06 am

your stock corvette has a rather marginal cooling system if your engines been modified for significantly higher hp levels, that cooling system can be significantly improved upon.I run into this frequently, and theres several sources or causes for an engine to run hotter than you might want it to,and cures, obviously you'll need to check fluid levels and your ignition timing.
Your Corvette’s main cooling fan is controlled by the PCM. The PCM sends a ground signal to the fan relay when it sees the desired temperature from a sensor to run the fan has been met. You need to check the sensors and fan relays and make sure you are getting your battery 12V and ignition 12V when the key is on. get a shop manual, and a bulti meter youll need them, now with the key on, jump the ground wire in the relay. If the fan turns on, you have an issue in the PCM and it may be time for a rebuild. If it does not turn on, then your problem lies in the fan circuit between the relay and the fans.
keep in mind a corvette draws air from under the car so its prone to pick up a good deal of street trash like leaves and plastic bags , so inspect and clean off any trash in the radiator fins before you assume the systems defective
also be aware that you can attack the heat control issues you might have from two directions, you can concentrate on removing heat from the engine more effectively with a larger more efficient radiator, bigger fans,, adding an alternator that allows more AMPS to spin those fans , adding more effective duct work, adding oil coolers, transmission coolers or a larger capacity baffled oil pan, adding heat exhaust vents to the hood,adding additives to the coolant that reduce the tendency to boil, like WATER WETTER, etc. or you can concentrate on reducing the heat generated thru control of your fuel/air mix ratio, ignition advance curve, timing and exhaust restriction.Id also point out that chevy water pumps can be purchased that are designed to spin in either clock wise or counter clock wire rotation and installing the wrong part number will cause big problems
obviously the first step in testing an over heating issue would be to verify the coolant and oil levels and verify the fans turn on and the water pumps pushing fluid thru the engine, and your not dealing with a defective t-stat or clogged radiator.
if those are correct it may be a sensor or tuning issue so verify sensor outputs with a good multi meter.
just a point many guys seem to over look, the fans run on electricity and a higher amp capacity alternator provides a good deal more current to spin those cooling fans, Ive seen several cars with marginal cooling that had that cooling issue disappear once a 160-200 amp alternator replaced the stock alternator, the increased current allowed the cooling fans to spin a good deal faster at low engine speeds and the result was more efficient cooling.

The key to C4 electrical is the checking for good solid low ohm resistance GROUNDS. They control almost everything, as sensors complete grounds or sense resistance. Voltage takes a backseat to good low ohm resistance grounds on these cars.
Locate the ground bundle of 5 wires on a bolt near the oil filter. (G104-107) Clean and repair. Also clean and repair the hot wires to the jumper post behind the battery.

Check the connections on the various temp sensors/switches. There is a different sensor for the gauge than the ecm or fan control. Some cars have as many as 4 or 5 temp sensors. What you see on the dash is not always what the ECM is seeing.

buy a CHEVY SHOP MANUAL FOR YOUR YEAR CORVETTE!
a logical step by step approach will lead you to the problem, youll be amazed at what youll learn reading links. use of a shop manual and multi meter can be very helpful,the cooling system tests are listed in shop manual book 2 of 2 in section engine controls 6-640 thru 6-645
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http://www.harborfreight.com/5-in-1-dig ... 98674.html
[b]learn to use the factory shop manual, and a multi meter


[b][size=150][color=#004080]
READ THRU THIS THREAD AND SUB LINKS

viewtopic.php?f=80&t=728&p=1025&hilit=sensors+camaro#p1025
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https://www.youtube.com/watch?v=vTl6UNMKjLc
the coolant temp sensor for the PCM is on the water pump a black and a yellow wire.

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http://tech.corvettecentral.com/2011/02 ... fications/

http://www.dbelectrical.com/casearch.as ... ageSize=60

http://members.shaw.ca/corvette86/Cooli ... ontrol.pdf

http://www.dbelectrical.com/p-9594-alte ... -1993.aspx

http://forums.superchevy.com/corvette-f ... mediately/

http://www.dbelectrical.com/p-3478-ford ... t-101.aspx

http://www.hotrodlane.cc/NewTPI%20links ... ml#tpitech

viewtopic.php?f=32&t=2697&p=7100#p7100
http://www.justanswer.com/uploads/carfi ... vette1.pdf

http://www.justanswer.com/uploads/carfi ... vette2.pdf

http://www.racerpartswholesale.com/prod ... cessories2

http://tech.corvettecentral.com/2011/02 ... fications/

http://www.racerpartswholesale.com/prod ... cessories2

http://www.summitracing.com/parts/prf-30111/overview/

http://www.stewartcomponents.net/Mercha ... Code=Therm

http://www.racerpartswholesale.com/prod ... cessories2

http://www.chevythunder.com/cts_diagnostics.htm

http://www.chevythunder.com/cts_diagnostic_pg2.htm

http://tech.corvettecentral.com/2011/02 ... fications/

http://members.shaw.ca/corvette86/Cooli ... ontrol.pdf

http://www.youtube.com/watch?v=X3IinhYkAP8


viewtopic.php?f=80&t=728&p=9217&hilit=sensor+mass#p9217

http://aspwholesale.com/index.php?act=v ... uctId=5159

viewtopic.php?f=57&t=149
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THE DIAGRAM ABOVE HAS THE CORRECT WIRE COLORS
heres a bit of info I found posted elseware
" Next on the order of useless LT1 items is the 160 degree thermostat. GM made the LT1 engine run very hot, temperatures of 230 degrees are not at all uncommon. These hot temperatures promote reduced emissions and a cleaner burn. Research has also shown that engine wear is related to temperature and that too low a temperature can cause premature engine wear. The stock thermostat in an LT1 is 180 degrees, the only reason the car runs so hot is that the computer controlled fans allow it to do so. From the factory the cooling fans are not programmed to come on until the vehicle approaches 240 degrees. While the vehicle is moving temperatures are easily maintained near 180 degrees, the temperatures only climb when the car sits at idle. If one so desires the computer can be reprogrammed to turn the cooling fans on at a much lower temperature, it is possible to maintain a temperature of below 200 degrees with the stock thermostat in place. The question then becomes, why does the engine need to run cooler? Racers have long known that cooler air is denser than hot air, denser air means more fuel and more fuel and air means more power. So if the engine is kept cooler it doesn't heat up the incoming air charge as much and more power is made. The theory is sound and very much proven, but the LT1 throws a small wrench in the theory. Because of the nature of the LT1's reverse flow cooling system the intake manifold does not have coolant flowing through it. So although the LT1 intake still gets plenty hot, it does not vary with respect to coolant temperature nearly as much as a traditional intake manifold does. The result is an engine that is far less sensitive to it's own temperature as far as horsepower is concerned. I would not have believed this myself until I tried an experiment at the dyno. I iced down my intake until it was actually cold to the touch. I then proceeded to make back to back dyno runs until the car was very hot. From this experiment I found that there was absolutely no reduction in power output until engine temperature exceeded 230 degrees, a condition that will never occur as long as there is sufficient airflow over the radiator. As such I can say with certainty that a 160 degree thermostat makes no difference in power. I cannot prove the lower temperature thermostat increases engine wear, but at the very least it decreases your heater output in the winter. "

obviously you'll want to put the car up on a lift and clean out the radiator fins both in front and behind as the cars tend to vacuum up road trash, blocking air flow.
your fans are controlled by sensors and the ECU, so you might want to install a sensor that turns the fan on as soon as the car reaches about 180F rather than the stock 230F.

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swapping to a 140-160-200 amp alternator makes a very noticeable difference in fan speed in some cars
http://www.dbelectrical.com/p-4436-corv ... -7888.aspx

http://www.ecklerscorvette.com/corvette ... -1995.html

viewtopic.php?f=36&t=1169

http://store.alternatorparts.com/extrem ... ifier.aspx

those temp switches come in a variety of temp ranges

http://www.summitracing.com/parts/HFM-ZFSWF/

185 f sensor
http://www.racerpartswholesale.com/prod ... cessories2

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IF YOU DON,T HAVE THE SHOP MANUAL , AND YOUR HAVING COOLING ISSUES,THIS IS AN EXCELLENT TIME TO BUY ONE, BECAUSE THE SENSORS AND WIRING AND RELAYS ARE NOT EASILY TRACED & TESTED WITHOUT THE MANUAL
obviously your engines tune, air/fuel ratio and ignition timing have a large effect on your cars operation temperature,moving the coolant thru the block efficiently and allowing the heat to rapidly dissipate, to the outside air flow with an efficient large capacity aluminum radiator will greatly improve the cars cooling.
the stock radiator is barely adequate for an engine putting out significantly more power as more hp creates more heat.
a stock transmission cooler won,t keep up with an aftermarket high stall converter, if you drive the car hard either.
One factor many guys overlook is that the SENSORS and RELAYS controlling the fans and the VOLTAGE the ALTERNATOR supply's to the car have a huge effect on both when the fans kick on and how fast they spin, which in turn has a major effect on the low speed air flow thru the radiator
keep in mind a great deal of the heat in a radiator is generated by the transmission fluid cooling, requirement on auto trans cars so adding a large AUXILIARY trans cooler helps a great deal, if you add an engine OIL COOLER that further reduces the heat load on the radiator
keep in mind that the standard C4 corvette uses a REVERSE rotation water pump, and its not a true high volume design, aluminum water pumps will reduce weight on the front of the car,so think about that when selecting a water pump
Here are some causes of overheating:

* Bad Thermostat or clogged t-stat
* Cooling system leaks/low coolant levels
* mixing two non-compatible anti-freeze types
* defective or the wrong water pump
* Leaky Head Gasket
* vacuum leaks in intake
* wrong fuel/air mix ratio
* incorrectly installed belts
* crud blocking the airflow thru radiator
* blocked or restricted air flow,missing duct work
* defective sensors or connections too sensors
* slime or sediment in radiator tubes
* one or both Fans Not Working correctly
* Leaky Water pump
* defective fan relays
* blown fuses
* over heated transmission coolant
* low alternator voltage
* low oil levels in engine
* incorrect ignition timing
* partly blocked catalytic converters
* Lower Radiator Hose Collapsing
* *Slipping Belt - Check belt tension and condition. A loose belt that slips may prevent the water pump from circulating coolant fast enough

Your engine may not be overheating at all. Your temperature gauge or warning lamp may be coming on because of a faulty coolant sensor. Sometimes this can be caused by a low coolant level or air trapped under the sensor.

READ THIS THREAD
viewtopic.php?f=57&t=149&p=1078&hilit=t+stat+drill#p1078
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WATER PUMP
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a quality radiator will be made from aluminum and have large cross flow tubes, read thru the links below,
theres several dozen sources but the better brand names, tend to have a better quality product than the cheaper imported versions

RADIATOR
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OIL PAN & OIL COOLER
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If your wiring up an aux electric fan ,yes I know your likely to just use the 14 ga or 12 ga you have, but after you do feel the wire after the fans run for 15 minutes and youll see why I strongly suggest 10ga stranded wire on any aux fan application
[color:red]
look thru this linked info, the links help[/color]

viewtopic.php?f=70&t=3504&p=9220&hilit=relay#p9220

viewtopic.php?f=50&t=3110&hilit=relay

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http://www.harborfreight.com/3-1-2-half ... 95670.html
TRANSMISSION COOLER
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many guys fail to realize that the combo of a high capacity baffled oil pan and an oil cooler can remove a great deal of your engine heat before the radiator, and coolant in the engine ever needs to start absorbing and transferring that heat to the outside air flow , ITS, high volumes of OIL FLOWING over the valve train and thru the bearing clearances and lubricating the rotating assembly , that is cooling many of the hotter components, and keeping that oil cool and flowing over those components is your first layer of defense on cooling the engine. its the volume of oil , and how effectively you keep the oil temps stable in the 210F-240F ranges and the quality and how well the oils filtered,more than the pressure that's important to your engines durability

heres some RELATED THREADS, with MUCH MORE DETAILED INFO

viewtopic.php?f=57&t=176

viewtopic.php?f=57&t=853

viewtopic.php?f=57&t=149&p=9344&hilit=+thermostat#p9344

viewtopic.php?f=54&t=3536

viewtopic.php?f=54&t=65

viewtopic.php?f=57&t=1540

viewtopic.php?f=80&t=728

viewtopic.php?f=57&t=755

viewtopic.php?f=57&t=832

viewtopic.php?f=87&t=11043&p=48999#p48999

viewtopic.php?f=57&t=2538&p=6583&hilit=+alternator#p6583

viewtopic.php?f=57&t=574

viewtopic.php?f=36&t=3222&p=8575&hilit=alternator#p8575

viewtopic.php?f=80&t=728&p=8392&hilit=cooling+fans%E2%80%A6#p8392

http://www.racerpartswholesale.com/prod ... cessories2

http://tpiparts.net/90_92_speed_density_sensors/

viewtopic.php?f=55&t=8961&p=31945#p31945

viewtopic.php?f=36&t=3222&p=8575&hilit=testing+alternator#p8575

viewtopic.php?f=70&t=355&p=13196&hilit=+alternator#p13196

http://tpiparts.net/85_89_maf_sensors/

keep in mind theres DOZENS OF DIFFERENT CHEVY TEMP SENSORS, for OIL AND COOLANT AND AIR, SO BE SURE YOU SELECT THE ONE DESIGNED TO MATCH YOUR GAUGE AND APPLICATION
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OPERATION
The electric cooling fan(s) are controlled by the PCM. The PCM controls the ground path for the three cooling fan relays. The relays are used to control the high current flow to power the cooling fan motors. Both fans operate together. When minimum cooling is required, the PCM energizes cooling fan relay #1 and both fans operate at low speed, since the fans are connected in series through cooling fan relay #3, and cooling fan relay #2 is open. When maximum cooling is required, the PCM energizes all three cooling fan relays. The left fan is still powered through cooling fan relay #1, but is now grounded through cooling fan relay #3. The right fan is now powered directly through cooling fan relay #2 and both fans operate at high speed.

LOW SPEED FANS
The cooling fans are controlled by the PCM based on inputs from the A/C system, Engine Coolant Temperature (ECT) sensor and Vehicle Speed Sensor (VSS).

The PCM will command low speed fans "ON" when Engine Coolant Temperature (ECT) is above 108°C (226°F). The PCM will turn the fans "OFF" when the temperature drops about 3°C (5°F). The minimum "ON" time for low speed fans is 50 seconds.

HIGH SPEED FANS
The PCM will command high speed fans "ON," when any of the following conditions exist at idle.




Certain Diagnostic Trouble Codes (DTCs) set.
ECT above 113°C (235°F).
A/C head pressure above 248 psi.
If the high speed fans were turned "ON," by the ECT, the PCM will switch the fans back to low speed when the temperature drops about 3°C (5°F). Minimum "ON" time for HI speed fans is 30 seconds.
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86-89 fan wiring
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GENERIC VERSION(above)
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HIB POSTED THIS
"A 96 has two fans. Both run at the same time. The fans have two speeds low and high. When low fans are commanded the fans are wired in series. When high fans are commanded they are wired in parallel. There are three fan relays which operate the fans and which are controlled by the ECM.

"Low fans" is commanded by the ECM when either: certain DTCs are set, ECT is above 219°F, engine oil temp is above 270°F or A/C head pressure is above 189 psi. Also, when engine speed is over 3500 rpm and oil temperature is over 261°F low fans will come on. The fans will go off once CT drops about 11°F. If A/C head pressure kicks the fans on, it must drop to 150psi before the ECM will shut them off. Min. on time is about 50 seconds

IVE SEEN THIS INFO POSTED BUT NEED TO VERIFY IT


Go to the fan relays on the driver side of the radiator support. You will find the little green wires going into the relays are the ground signals from the computer to trigger the fan. Splice in a hard ground to the frame, and the fans will run as soon as you turn on the key, regardless of temp.


"High fans" is commanded by the ECM when either: certain DTCs are set, ECT is above 228°F, engine oil temp is above 277°F or A/C head pressure is above 225-psi. Also, when engine speed is over 3500 rpm and oil temp is over 266°F, the ECM will request high fans. The ECM will turn off high fans once coolant temp drops about 11° or A/C head pressure drops below 189 psi.

If you saw 260 on the digital display and the coolant boiled over, obviously the car was way overheating. If you ran the car like that for any length of time, engine damage is possible. Hopefully that's not the case.

I'd be looking for cooling system problems other than just the fans such as restricted air flow through the cooling stack. Also, overheating really stresses cooling system parts such as radiator hoses, heater hoses, belts, radiator caps and so forth. Considering the car is 15 years old, if those parts are original, I'd carefully inspect them for damage.

But, again, the best way to troubleshoot the cooling fans on a 90-96 is using the diagnostic table in the Service Manual. "
IF YOU CAN,T SMOKE THE TIRES AT WILL,FROM A 60 MPH ROLLING START YOUR ENGINE NEEDS MORE WORK!!"!
IF YOU CAN , YOU NEED BETTER TIRES AND YOUR SUSPENSION NEEDS MORE WORK!!
grumpyvette

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Re: cooling off that c4 corvette

Postby grumpyvette » November 26th, 2010, 7:57 am

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LOW READING
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HIGH READING
one of the least well known causes of over heating is an alternator that doesn,t put out enough power to spin the fans fast enough to cool the car at low speeds where theres little or any air flow thru the radiator due to car movement,and the pressure of the air in front of the car at higher speeds.
theres no reason you can,t convert to a 200 amp or one wire alternator if you do the required modifications to your wiring in the car, read this
http://www.madelectrical.com/electrical ... wire.shtml

these guys sell an alternator Ive used on several corvettes with excellent results, you'll usually notice the car runs a bit smoother and the fans seem a bit louder because both the ignition and fans get more consistent power
http://www.db-starter-alternator.com/c- ... 0-amp.aspx

http://tech.corvettecentral.com/2011/02 ... fications/

http://www.mamotorworks.com/corvette-c4 ... -6128.html


one wire
http://www.db-starter-alternator.com/c- ... 0-amp.aspx


viewtopic.php?f=36&t=1169&p=5267&hilit=corvette+alternator#p5267


oil flow, not coolant does the first heat transfer from the critical bearings,rings,rockers,springs,ETC. oil flow must remain constant and under enought pressure to always provide a film between the moving metal parts, a high capacity oil pan in the 7qt-9qt range and windage control system for the oil helps a great deal with engine cooling.
I have repeatedly said that your oil temp should keep above 215° to allow moisture to burnout of the oil and that your coolant temp should stay in the 180-220 range
SMOKEY YUNICK, in several places in several books, refers to extensive dyno testing he did for General Motors, where they consistently found, that both engine wear and hp production benefited when the oil temp stayed above 215° but below 240°, and the coolant temperature stayed between 180 and 220, degrees, or as SMOKEY said, trying keep your oil hot, but your coolant, about 20 to 30° lower in temperature but the coolant should never be below 180°, and should not exceed 220°, while temperature should never below the below 215°, and 235 to 240 is about ideal, mineral base oils tend to start breaking down over 240°, synthetic oils can easily handle temperatures up in the 270 degree range in for extended periods, but they performed best in their lubrication in cleaning function went down in the 240 range


I normally buy oil pans from these guys as they are good quality for the money

http://www.parts123.com/PartFrame.asp?ZTM=cadefjgb&GHOME=www.midwestmotorsportsinc.com&TITLE=Midwest_Motorsport

http://forum.grumpysperformance.com/viewtopic.php?f=57&t=853

i don,t usually have alot of money to waste so I normally buy this #KEV 1090 oil pan for $100 and weld a sump extension forward
with this kit they sell for $26 # MWM 15900
and add a windage screen #MIL 32250 for $80,so for about $220-$245 you can have a baffled 9.5 qt oil pan with windage screen
http://www.moroso.com/catalog/categorydisplay.asp?catcode=11330
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while I tend to build or modify my personal oil pans
MOROSO has a good product, in several versions,
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which I can recommend if your buying one!


you will need to carefully measure clearances for the cross member,suspension,headers,starter,oil filter, ground clearance, ETC. before ordering , or modifying an oil pan

restricting coolant flow speeds to help cooling is a MYTH,started when guys found that removing the thermostat could cause overheating on some cars, the thermostat did not restrict the flow significantly but it did tend to prevent the waterpump from cavitateing and failing to efficiently move coolant.
large tube aluminum radiators tend to cool very effectively

mounting an electric push fan infront of your radiator can significantly help lower temps

water wetter additive can disolve some types of paper thermostat gaskets

a 17lb radiator cap is about as high a pressure rating as you can use on a standard cooling system

air flowing over the outter surface of a road racing style, 8qt or larger extended sump oil pan removes a good amount of heat from the engine, tall valve covers can also act to radiate heat from the oil running over the inner surfaces

header coatings can also help reduce under hood temps

naca ducts or side vents that allow efficient removal of air flow behind the radiator can help cooling





YES YOU SHOULD RUN A THERMOSTAT, about 180F-190F prefered on most high performance cars


FACTORS THAT IMPEDE COOLING EFFICIENCY


1 - Coolant does not pass through radiator freely. Over time, chemical reactions can cause corrosion buildup in the radiator tubes and can restrict the flow of coolant through the radiator. Also, debris can accumulate at the tube openings (similar to a strainer) and the resulting blockage can restrict flow. The result is that the heat is not transferred from the coolant to the fins and overheating will likely occur.

2 - Air flow is restricted through the radiator and heat cannot be dispersed into the air. If trash or bugs clog the fins on the radiator, then the air flow cannot pass over the fins and the heat is not dispersed into the air. The buildup of heat can cause overheating.

3 - Deterioration. Over time, the metal fins oxidize and deteriorate. Road salt and salty air from coastal areas contribute to speeding up the oxidation process of radiator fins.

http://www.jcwhitney.com/productnoitem.jhtml?CATID=5131&BQ=jcw2 Image Image RADIATOR CORROSION INHIBITOR Prevents overheated radiators caused by rust, scale and corrosion. Save money on needless flushing, repairs, anti-freeze changes, special additives! Zinc anode slips in radiator filler neck and neutralizes rust/corrosion-causing chemicals. Lasts for years. NOTE: Not for radiators with plastic tanks. http://www.pjhbrands.com/vht/coppergasketcement.htm
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http://www.radcapproducts.com/order.html" http://www.radcapproducts.com/order.html Image



if you don,t read the links youll miss most of the info!

http://www.radiatorbarn.com/

http://www.streetrodstuff.com/Products/157/

http://www.streetrodstuff.com/Articles/Cooling/More_Cooling_Suggestions/

http://www.streetrodstuff.com/Articles/Cooling/Cooling_Suggestions/

http://www.prenhall.com/autoweb/chekchart/classch5.pdf
IF YOU CAN,T SMOKE THE TIRES AT WILL,FROM A 60 MPH ROLLING START YOUR ENGINE NEEDS MORE WORK!!"!
IF YOU CAN , YOU NEED BETTER TIRES AND YOUR SUSPENSION NEEDS MORE WORK!!
grumpyvette

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Posts: 14105
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Re: cooling off that c4 corvette

Postby grumpyvette » April 15th, 2011, 8:39 pm

in an ideal world the coolant temp would stay in the 190F-200F range, install a 180F-or-190F t-stat and have the fans reprogramed to come on at about 185F-200F and youll see a marked stabilization of the coolant temp IF everythings functioning CORRECTLY

heres the fan control kits

185F

http://store.summitracing.com/partdetail.asp?part=SUM-890015

200F

http://store.summitracing.com/partdetail.asp?autofilter=1&part=PRF%2D30102&N=700+115&autoview=sku

personally I sellected the 190F T-stat 185F fan control , but IM seriously thinking of getting the 200F fan control simply because with my external trans cooler the engine oil temp seldom gets over 220F and it takes 215F to burn off all moisture in the oil
theres INSTRUCTIONS with the kit, but basically you install the sensor and wire in any fan you choose to , following those instructions and using the new sensor. you can use the original fan, but in most cases a larger aftermarket fan or an additional transmission cooler is used. the sensor screws into the cylinder head

you can also install just an aftermarket fan
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http://store.summitracing.com/partdetail.asp?autofilter=1&part=FLX%2D365&N=700+115&autoview=sku

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http://store.summitracing.com/partdetail.asp?autofilter=1&part=HFM%2DZFB16S&N=700+320174+4294775279+115&autoview=sku
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http://store.summitracing.com/partdetail.asp?autofilter=1&part=DER%2D13720&N=700+115&autoview=sku

http://store.summitracing.com/partdetail.asp?autofilter=1&part=DER%2D15800&N=700+115&autoview=sku


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http://store.summitracing.com/partdetail.asp?autofilter=1&part=PRM%2D12318&N=700+115&autoview=sku
IM currently using this on my 1985 corvertte but have used others in the past

IF YOUR ON A REALLY LIMITED BUDGET, TAURUS FANS FROM A SALVAGE YARD CAN NORMALLY BE FOUND DIRT CHEAP........HERES INFO LARRY POSTED

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"The two diagrams above show how to build and wire an auto relay switched 2-speed FORD TAURUS fan.
Parts needed......10 guage wire for the power circuit. 18 guage wire for the control cicuit.
Three relays..... 1) High speed relay, Tyco VF7-12V,70amps
2)Low speed relay and Aux relay, standard BOSCH relays
Two switches,,,,.1)Low speed temp. switch- Adj. Flexilite, FLX-31147 from SUMMIT.
2)High speed temp. switch from Standard Motor Products, TS-158 or TS-392.
I put the adj. low speed switch and the three relays in seperate relay boxes and mounted them in the engine comp. The high speed temp switch I mounted where one of the heater hoses went. Est. cost of parts, less the fan, is $50.00 . 10 guage wire is used in the power circuit and 18 guage in the control circuit. The 12V switched control circuit can be connected to any live connection with ignition on.
The control circuit shown is as follows..... When the temp. reaches your set low speed figure, let's say 190 deg.the low speed relay is energized thru pin 86, 85 connects to 87A of the AUX relay and pulls 30 of that relay, 87 of the low speed relay and 30 are closed sending power to the fan to run at low speed.
When the temp. reaches your high speed switch figure, let's say 210 deg. pin 86 of the AUX. relay energizes thru 85 and 30 releases from 87A of the low speed relay and connects with 85 of the high speed relay which thru 87 of that relay powers the fan to run at high speed.
ARE we confused yet?????
When the temp falls below the high speed swich figure the AUX relay will switch back to the low speed relay.
Therfore low and high speeds will never be on at the same time and you will have the following conditions...
1) No fan on.
2) Low speed on.
3) High speed on."

http://forum.grumpysperformance.com/viewtopic.php?f=70&t=355

http://www.powerstream.com/Amps-Watts.htm

read thru this link
IM always amazed at the lack of research many guys do before purchasing components, who then are stunned and amazed to find that those components won,t work correctly without further upgrades to the electrical system, and can,t figure out why the battery drains .
example
you decide you need a 800 watt sound system, and your find the car misses and runs hot??
thats odd theres no obvious connection between the car missing or over heating an adding a better sound system< OR IS THERE? and your installing it in your car when the tech suggests you might want to install a larger more powerful alternator.......IS he correct? do you need one?

Converting Watts to Amps

The conversion of Watts to Amps is governed by the equation Amps = Watts/Volts

For example 12 watts/12 volts = 1 amp

so 800 watts/12 volts =67 amps

now its a sure bet that the stock alternator that puts out about 90-110 amps (depends on year) and that the basic electrical system requires almost that current flow to function,without the additional equipment additions,will require an upgrade!
so yes! only an optimist would even think, for an instant that the stock alternator would keep up with the increased current draw, of that 800 amp sound system, the tech guys who are bound to suggest a larger alternator be installed are correct, you'll want to install a 150-amp 200 amp alternator like the one linked to above in this thread
failure to do so reduces the voltage/amps to the ignition and cooling fans under some conditions.
the high output alternator will require a larger gauge cable between the alternator power out and the battery positive terminal and adding an additional larger gauge ground to the engine/frame/battery negative sure won,t hurt

http://www.jegs.com/i/Edelbrock/350/1792/10002/-1
Image
look at the chart above ,related to an edelbrock electric fuel pump, while that particular pump may not be what youll be using all electric pumps will be some what similar in that fuel volume and pressure output varies with current draw,and the stock alternator in most cars is semi ,marginal at supplying the required current under some conditions.
swapping from a stock 105 amp alternator to an aftermarket 180 amp-200 amp alternator has consistently made a noticeable difference in cooling fan speed and at times fuel pressure.
it should be rather obvious that as the alternator current produced increases theres a potential for the the cars fuel pump output to increase ,especially if the current battery or alternator is marginal under full loads
one factor I seldom see being mentioned is that the alternator output in amps and volts has a very measurable effect on the cars electrical cooling fans, and electric fuel pump pressure delivered to the engines fuel rail, or carburetor inlet, especially if you don,t have a dependable return line style fuel pressure regulator and a fuel pump that easily provides more than enough pressure and volume of fuel at the minimum volts and amps the cars alternator and charging system provides.
Ive repeatedly seen the cooling fans run more efficiently and the ignitions run more consistently with a larger amp rated alternator.

http://www.dbelectrical.com/c-4913-200-amp.aspx
Couple formulas:
Power(Watts(equipment rating))=Volts x Amps
Amps= Watts divided by Volts
Volts= Watts divided by Amps

READ THE SUB LINKS
http://www.enginebuildermag.com/1998/03 ... nt-output/

http://www.highoutputalternator.com/Tec ... ulator.htm

http://jgdarden.com/batteryfaq/carfaq5.htm

check your alternator's current easily ,as its output-can be verified and tested, many auto electrical places and some like Autozone will load-test your battery and alternator for free with a heavy tester.

oil cooler fans
viewtopic.php?f=80&t=10514&p=44478&hilit=corvette+alternator#p44478

head lights
viewtopic.php?f=36&t=160&p=39154&hilit=corvette+alternator#p39154

radiator cooling fans
viewtopic.php?f=32&t=3954&p=27005&hilit=corvette+alternator#p27005

alternator
viewtopic.php?f=70&t=6961&p=22863&hilit=corvette+alternator#p22863

viewtopic.php?f=36&t=3222&p=8575&hilit=test+alternator#p8575
IF YOU CAN,T SMOKE THE TIRES AT WILL,FROM A 60 MPH ROLLING START YOUR ENGINE NEEDS MORE WORK!!"!
IF YOU CAN , YOU NEED BETTER TIRES AND YOUR SUSPENSION NEEDS MORE WORK!!
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Re: cooling off that c4 corvette

Postby grumpyvette » October 12th, 2011, 1:01 pm

look I'm old enough t to realize that theres ALWAYS someone smarter or more experienced than I am at darn near everything, but I,m also rather experienced and have a very good background in most types of mechanical and electrical and automotive engineering, but that hardly means i never over look things so here's a chance to show your skills.

I want to significantly lower the temperature that my 1996 corvette coolant OCCASIONALLY circulates at, Ive already got an electric fan cooled oil and transmission fluid cooler and a custom built 10 quart baffled oil pan and a new aluminum radiator and high volume water pump, but My goal here is to maintain coolant temps at or slightly below 210f and oil temps at or below 220F even when running the engine hard
frankly the oil has a hard time reaching 215F and trans fluid stays at about 180f so they are not the problem, but the coolant temps do jump to 245f if I run the car hard, they drop rapidly once I slow down but I would prefer they never get over 210F.
Ive got a 180F t-stat, but keep in mind the T-stat only controls when the coolant flows, and in my case Ive drilled 8 3/32" holes in the flange so its not a major factor here, I don,t think simply running higher rpms under load (IE pulling 5500-6300rpm in top gear for a few minutes constitutes abuse) and Ive checked the ignition timing advance curve and checked the plugs ,and measured the fuel/air ratio, everything looks well within safe limits, its simply not cooling as efficiently as Id like.it looks like the obvious answer I'm trying to ignore is that I just need to buy a bigger more efficient radiator
so any ideas are welcome as to for example turning the fans on at 180F, or installing a larger more effective fan(S) or darn near any good ideas you might have,
its been doing this occasionally since I built it, but I rarely run the car at those speeds so its a very low priority to correct since its got zero effect on driving the car under 120 plus mph which of course is rarely done, its just that every once in a while I decide to tackle minor problems.
Ive posted my basic engine combo before, its been thru some minor changes since this posted config but this is the basics

viewtopic.php?f=32&t=430


BTW FAULTY GROUNDS, IN MANY CARS AND ESPECIALLY NEWER CORVETTES CAUSE MANY ELECTRICAL ISSUES SO IF YOU HAVE INTERMITTENT ELECTRICAL ISSUES CHECK THEM CAREFULLY
Image
IF YOU CAN,T SMOKE THE TIRES AT WILL,FROM A 60 MPH ROLLING START YOUR ENGINE NEEDS MORE WORK!!"!
IF YOU CAN , YOU NEED BETTER TIRES AND YOUR SUSPENSION NEEDS MORE WORK!!
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Re: cooling off that c4 corvette

Postby Indycars » October 12th, 2011, 3:27 pm

grumpyvette wrote:look I'm old enough t to realize that theres ALWAYS someone smarter or more experienced than I am at darn near everything, but I,m also rather experienced and have a very good background in most types of mechanical and electrical and automotive engineering, but that hardly means i never over look things so here's a chance to show your skills.

I want to significantly lower the temperature that my 1996 corvette coolant OCCASIONALLY circulates at, Ive already got an electric fan cooled oil and transmission fluid cooler and a custom built 10 quart baffled oil pan and a new aluminum radiator and high volume water pump, but My goal here is to maintain coolant temps at or slightly below 210f and oil temps at or below 220F even when running the engine hard
frankly the oil has a hard time reaching 215F and trans fluid stays at about 180f so they are not the problem, but the coolant temps do jump to 245f if I run the car hard, they drop rapidly once I slow down but I would prefer they never get over 210F.
Ive got a 180F t-stat, but keep in mind the T-stat only controls when the coolant flows, and in my case Ive drilled 8 3/32" holes in the flange so its not a major factor here, I don,t think simply running higher rpms under load (IE pulling 5500-6300rpm in top gear for a few minutes constitutes abuse) and Ive checked the ignition timing advance curve and checked the plugs ,and measured the fuel/air ratio, everything looks well within safe limits, its simply not cooling as efficiently as Id like.it looks like the obvious answer I'm trying to ignore is that I just need to buy a bigger more efficient radiator
so any ideas are welcome as to for example turning the fans on at 180F, or installing a larger more effective fan(S) or darn near any good ideas you might have,
its been doing this occasionally since I built it, but I rarely run the car at those speeds so its a very low priority to correct since its got zero effect on driving the car under 120 plus mph which of course is rarely done, its just that every once in a while I decide to tackle minor problems.
Ive posted my basic engine combo before, its been thru some minor changes since this posted config but this is the basics

viewtopic.php?f=32&t=430


You got to be able dissipate the same number of BTUs from the coolant thru the radiator that the engine is putting into the coolant. To do that several factor are involved, coolant flow, air flow and radiator surface area. Have you verified that the high volume water pump is indeed moving the volume of water it was designed for, maybe it's partially defective and only moving ~70% of the volume required for sustained 6000 RPM ??? Which would be good enough for normal driving, but not enough for the higher loads.

Could the water pump be cavitating at the higher RPMs and short burst in a drag race situation would NOT be long enough for the problem to show up, but at a sustained high RPM, the radiator is getting behind. Besides air in the coolant will not cool as well as a straight liquid. A defective impeller or a restriction on the input to the pump could cause this.

The Vette does not have much frontal area for picking up air for the radiator. Maybe a larger air damn is needed to increase the volume of air moving thru the radiator at high speeds. Also if you can't get the air out of the engine bay, then you can't get it in thru the radiator. I don't know about the underside of your Vette, but if it has shrouds stopping the air flow from going underneath the car for aerodynamic reasons, then the air maybe piling-up in the engine bay and slowing down the air flow thru the radiator. If so, could you remove a shroud to see if that increase the air flow???

The fans are never going to move as much air as the car would pickup moving at 70+ MPH, if anything they would be a restriction to the air flow. To my way of thinking, the fans are needed when the car is stopped or moving slowly, maybe up to ~30-40 MPH.

Just my thoughts on the matter!
Rick
Too much is just enough!!!

- Check Out My Dart SHP Engine Project: viewtopic.php?f=69&t=3814
- Need a Dynamic Compression Ratio Calculator: viewtopic.php?f=99&t=4458
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Re: cooling off that c4 corvette

Postby grumpyvette » October 12th, 2011, 3:37 pm

thanks ! good info,

Ive been doing a few tests, it looks like a combo of both a bit too small of a radiator for the engine horsepower being produced and probably air flow restrictions thru the radiator at high car speeds , Ill look into both, id bet I can clear this little P.I.T.A. glitch up shortly, its just a minor deal as I can,t often run those mph long enough to even cause the problem.


BTW Hib Halverson posted this bit of info elseware
"A 96 has two fans. Both run at the same time. The fans have two speeds low and high. When low fans are commanded the fans are wired in series. When high fans are commanded they are wired in parallel. There are three fan relays which operate the fans and which are controlled by the ECM.

"Low fans" is commanded by the ECM when either: certain DTCs are set, ECT is above 219°F, engine oil temp is above 270°F or A/C head pressure is above 189 psi. Also, when engine speed is over 3500 rpm and oil temperature is over 261°F low fans will come on. The fans will go off once CT drops about 11°F. If A/C head pressure kicks the fans on, it must drop to 150psi before the ECM will shut them off. Min. on time is about 50 seconds

"High fans" is commanded by the ECM when either: certain DTCs are set, ECT is above 228°F, engine oil temp is above 277°F or A/C head pressure is above 225-psi. Also, when engine speed is over 3500 rpm and oil temp is over 266°F, the ECM will request high fans. The ECM will turn off high fans once coolant temp drops about 11° or A/C head pressure drops below 189 psi.

If you saw 260 on the digital display and the coolant boiled over, obviously the car was way overheating. If you ran the car like that for any length of time, engine damage is possible. Hopefully that's not the case.

I'd be looking for cooling system problems other than just the fans such as restricted air flow through the cooling stack. Also, overheating really stresses cooling system parts such as radiator hoses, heater hoses, belts, radiator caps and so forth. Considering the car is 15 years old, if those parts are original, I'd carefully inspect them for damage.

But, again, the best way to troubleshoot the cooling fans on a 90-96 is using the diagnostic table in the Service Manual. "
IF YOU CAN,T SMOKE THE TIRES AT WILL,FROM A 60 MPH ROLLING START YOUR ENGINE NEEDS MORE WORK!!"!
IF YOU CAN , YOU NEED BETTER TIRES AND YOUR SUSPENSION NEEDS MORE WORK!!
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Re: cooling off that c4 corvette

Postby Crepitus » October 12th, 2011, 10:34 pm

I have been looking at cooling / front down force on my C4. I want to move the battery to the pass side cubby hole behind the seat. That will open up room for a oil filter, cooler and fan discharging out the drivers side gills, behind the front wheel. I very much dislike the way header and general engine heat bakes the engine compartment after the car has stopped. I am thinking vents cut in the hood about 2" x 6" over each header, next to the hood scoop. this will allow engine heat out at low or no speed and at speed that should be a good low pressure area pulling air out from under the hood and improving down force. There are some high dollar hood vents offered by Gulstrad but I am looking a little (OK a lot!) less costly solution.

Do you guys think it might work?
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Re: cooling off that c4 corvette

Postby grumpyvette » October 13th, 2011, 8:10 am

thats a good idea,
if your more interested in true performance that keeping the car looking original, I've seen them used frequently on road racing car applications, and a correctly designed set of hood louvers will allow a good deal of engine heat to be more easily pushed out of the engine compartment and that tends to aid air flow thru the radiator also.
ducts are available in steel, stainless steel, powder coated steel, fiber glass and in dozens of shapes and designs, obviously youll need to measure how much room you have ant try to find a design that looks good and functions well, and theres also the option of fabricating something custom made, below is just a small sample of what you could do.

hood scoop related info
viewtopic.php?f=35&t=353&p=5243&hilit=hood+scoop#p5243

http://www.vetteweb.com/tech/vemp_0602_ ... ewall.html

http://www.hoodlouvers.com/shop/weld-in ... l-hi-flow/ the 9' x 14" will fit the two areas on the c4 hood rather well

viewtopic.php?f=55&t=8961&p=31945&hilit=hood+vents#p31945

http://www.twpinc.com/twpinc/products/T ... 7Qodw1qhHw

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http://secure.chassisshop.com/partlist/6015/

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http://www.hoodlouvers.com/products.html

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IF YOU CAN,T SMOKE THE TIRES AT WILL,FROM A 60 MPH ROLLING START YOUR ENGINE NEEDS MORE WORK!!"!
IF YOU CAN , YOU NEED BETTER TIRES AND YOUR SUSPENSION NEEDS MORE WORK!!
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Re: cooling off that c4 corvette

Postby Crepitus » October 14th, 2011, 10:00 pm

[/quote]Image[/quote]

Ya There she is...
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Re: cooling off that c4 corvette

Postby Crepitus » November 2nd, 2011, 11:12 pm

One more idea for cooling the C4s, a small air dam along the front side of the front wheel opening, only about 3/4 or 1" wide. Kinda like mud flaps only in front of the wheel. Will help pull air out of the wheel well. I can work even better if the top of the wheel well is removed. Any thing that helps air out from under the hood will improve cooling and front down force.
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Re: cooling off that c4 corvette

Postby grumpyvette » November 10th, 2011, 6:35 pm

LT1 Reverse Flow Cooling System
By Scott Mueller.

One of the greatest features of the '92 and up Chevrolet LT1 engine is the reverse flow cooling system. In fact it is reverse flow cooling that is truly the key to the incredible performance of the modern LT1. Reverse flow cooling is vastly superior to the conventional cooling systems used on virtually all other engines. This is because it cools the cylinder heads first, preventing detonation and allowing for a much higher compression ratio and more spark advance on a given grade of gasoline. A fringe benefit is that cylinder bore temperatures are higher and more uniform, which reduces piston ring friction. Because of this new cooling system, the LT1 can easily meet ever increasing emissions standards with significant gains in power, durability, and reliability.

Conventional Coolant Flow:

In a conventional engine design, coolant enters the front of the block and circulates through the block's water jacket. The coolant is first heated by the cylinder barrels, and then hot coolant is subsequently routed through the cylinder heads and intake manifold before returning through the thermostat to the radiator.

Because the coolant from the radiator is first directed to the cylinder bores, they run at below optimum temperatures which increases piston ring friction. The heads subsequently get coolant that has already been heated by the cylinder block, which causes the heads to run well above optimum temperatures. The hotter cylinder heads promote detonation (spark knock) and head gasket failures. To combat the increased tendency to detonate, compression ratios has to be lowered and spark advance reduced, which significantly reduces engine power output and efficiency.

Besides promoting detonation, causing gasket failures, forcing reduced compression, spark advance, and significantly reduced power output, a conventional cooling system causes several other problems. Since the thermostat is on the exit side of the system, it does not have direct control over the cold coolant entering from the radiator. This is especially true when the thermostat first opens after reaching operating temperature. As the thermostat first opens allowing hot coolant to exit the engine, a rush of very cold coolant enters the block all at once, shocking the engine and causing sudden dimensional changes in the metal components. The extreme thermal shock experienced by the engine causes head gaskets and other soft parts to fail much more quickly.

Conventional cooling system design also allows isolated engine hot spots to occur, which lead to the generation of steam pockets and coolant foaming. Coolant which is full of air and foam reduces cooling system performance and can even lead to engine overheating.

LT1 Coolant Flow:

The LT1 is completely different since it uses reverse flow cooling. The incoming coolant first encounters the thermostat, which now acts both on the inlet and outlet sides of the system. Depending on the engine coolant temperature, cold coolant from the radiator is carefully metered into the engine. This allows a more controlled amount of cold coolant to enter, which immediately mixes with the bypass coolant already flowing. This virtually eliminates the thermal shock present in the old system.

After entering through one side of the 2-way thermostat (at the appropriate temperature), the cold coolant is routed directly to the cylinder heads first, where the combustion chambers, spark plugs and exhaust ports are cooled. Then the heated coolant returns to the engine block and circulates around the cylinder barrels. The hot coolant from the block re-enters the water pump, and hits the other side of the 2-way thermostat, where it is either re-circulated back through the engine or directed to the radiator, depending on temperature.

All of this means that the thermostat housing is the INLET (opposite of most engines), while the water pump is the OUTLET. The water pump (outlet) on the engine runs to the top left (inlet) of the radiator. The lower right (outlet) of the radiator runs to the thermostat housing (inlet) on the engine.

This also means that the "upper" hose on the radiator would be connected to the water pump (mid/lower part of the engine) and is the outlet of the engine, so it should be hot with the thermostat open. The lower hose on the radiator is connected to the thermostat housing (upper part of the engine) and is the inlet to the engine.

The main concept behind reverse flow cooling is to cool the heads first, which greatly reduces the tendency for detonation, and is the primary reason that the LT1 can run 10.5 to 1 compression and fairly significant ignition advance on modern lead-free gasoline. Reverse flow cooling is THE KEY to the Generation II LT1s increased power, durability, and reliability over the first generation smallblock engine.

There are three main circulation systems for the LT1, while most engines only have two systems. As with most cars there is circulation through the heater core and the radiator, but there is a third system on the LT1 which includes steam vents in the head, along with a pressurized reservoir.

Coolant to the heater core comes from the water pump. The lower hose on the water pump is the heater core inlet, and should have a flow restrictor mounted in the hose. This is to prevent over-stressing the core at high engine rpms. The heater core outlet hose returns to the water pump at the upper hose connection, and also has a T-connector to the pressurized reservoir to bleed off any air.

Thermostats:

All LT1 engines utilize a special 2-way acting full bypass thermostat which can be seen in this photo: . Dual-acting means that the thermostat regulates coolant flow both in to as well as out of the engine, while the bypass portion of the thermostat circuit supplies the water pump with a full flow of liquid coolant at all times. This is unlike a conventional engine thermostat, which only regulates coolant flow at the engine outlet, and which does not allow full flow through the water pump when the engine is cold and the thermostat is in bypass mode.

Both sides of the 2-way thermostat used in the LT1 are linked together, and a single wax pellet actuator operates the spring loaded mechanism at a pre-set temperature. When the designated temperature is reached, the wax pellet expands, opening the dual acting valve. All current LT1s come from the factory with a relatively low 180 degree temperature thermostat. Most conventional engines today use 195 degree thermostats in order to meet emissions specifications at the expense of power, durability, and reliability.

It is important to note that the 2-way thermostat is unique to the Generation II LT1 and is not interchangeable with older Chevrolet smallblock engines. This is particularly important if you decide to change to a colder 160 degree thermostat, make sure it is the proper dual acting type required by the modern LT1. You can obtain the proper type in a 160 degree version from or .

Additional LT1 Cooling System Improvements:

In addition to reverse coolant flow, there are several other improvements in the LT1 cooling system over conventional engines.

Dry Intake Manifold:

The LT1 has absolutely NO water running through the intake manifold! Conventional cooling systems have passages in the intake manifold which allow coolant to crossover from one side of the engine to the other. In the LT1, coolant crossover occurs in the water pump, which is also where the thermostat is located. Since there are no coolant passages in the intake manifold, a major source of leaks has been eliminated. Overall engine reliability is improved since an intake manifold leak allows coolant to enter the top of the engine which can quickly wipe out the camshaft, lifters, and other major engine components. Designing a dry intake manifold without either coolant passages or a thermostat housing also allows a much lower profile. The LT1 engine is 87mm (nearly 3.5 inches) lower than the previous L98 Corvette engine.

Gear Driven Water Pump:

One big problem with conventional cooling systems is the water pump, which simply cannot last a targeted minimum 100,000 mile reliability figure without experiencing leaking gaskets or seal failures. This has traditionally been caused by the excessive side loads placed on the bearings and seals of a conventional water pump through the belt drive mechanism. In the LT1 this problem is solved by driving the water pump directly via a spur gear driven by the camshaft sprocket. This results in a dramatically more reliable water pump that should easily last 100,000 miles or more.

Since the water pump is no longer belt driven, the vehicle will still be driveable even if the serpentine belt fails. This is a major safety factor as it allows one to drive the partially disabled vehicle to the nearest service center.

Steam Vents:

The LT1 has strategically placed steam vents at the back of both cylinder heads. Since the heads are the hottest part of the engine, pockets of steam can be more easily generated there. The steam vents are connected together by a crossover vent tube at the back of the heads, which directs any steam and a small flow of coolant to the front of the engine where it flows through the throttle body, warming it for improved cold weather performance. After passing through the throttle body, most of the steam is condensed back into liquid coolant and returned to the system.

In LT1 B/D-cars, coolant exiting the throttle body is passed directly into a pressurized coolant reservoir where any air remaining in the coolant is completely scavenged. In LT1 F-cars, coolant from the throttle body connects to the heater outlet via a vented "tee" connector, where any trapped air in the system can be bled off manually. Eliminating steam pockets and foam in the coolant allows for more uniform cooling system performance, preventing hot spots and potential overheating.

Radiator Flow:

The radiator is a standard cross-flow type with coolant entering on the left and exiting on the right. Unlike a conventional cooling system, the thermostat housing is the inlet for the engine and is therefore connected to the outlet at the radiator. The upper left (inlet) side of the radiator is connected to the water pump (outlet) on the engine, and the lower right (outlet) side of the radiator is connected to the thermostat housing (inlet) on the engine. Flow through the engine is reversed, however flow through the radiator is conventional.

Precision Machined Thermostat Housing:

The thermostat housing is a precision machined component that fits directly onto the top of the water pump without a gasket. Instead, an O-ring is used to seal the thermostat inside the housing. This precision design reduces the tendency for leaks, plus it makes thermostat replacement a very simple job since there is no old gasket material to scrape off. Servicing is further simplified because the thermostat housing is situated directly on top of the water pump, and access is unobstructed. I dare say that the LT1 thermostat is the easiest to change I have ever experienced. Finally, an air bleeder valve is located on the top of the thermostat housing, which allows one to quickly and easily bleed out any trapped air after cooling system maintenance has been performed.

Some Tips For Replacing The Thermostat:

Follow the service manual procedure, but beware of a few things. One is that despite the drawing in the service manual, there is no gasket. There is an O-ring seal that goes around the thermostat itself, which should come with the thermostat.

Also beware that the factory manuals and any instructions written from them show an INCORRECT 21 ft-lb. torque spec. for the two thermostat housing bolts. Noting that these are tiny 5mm bolts in an aluminum housing, it was obvious to me that the specification was wrong (nearly three times too much), but I know several people who have tried to tighten to that spec, stripping both bolt holes instantly, requiring a helicoil repair.

ALL '94-'96 B-car and F-car manuals list this incorrect torque spec! The correct spec., which is reported in the updated '96 'vette manual is 89 in-lb. or 7.4 ft-lb. I'm surprised there are not more people busting these bolts or stripping out the threads in the aluminum water pump housing. GM should really issue a TSB on this!

A final concern is that you should pack the area below the thermostat housing and above the distributor with rags before undoing anything. The distributor is mounted low on the front of the block, behind and between the water pump and above the crankshaft, and you do not want coolant dripping onto the distributor. If any coolant enters the distributor, it will likely cause accelerated corrosion and require the distributor be repaired or replaced.

Low Operating Pressure:

The entire cooling system on the LT1 is designed to operate at lower pressures than conventional cooling systems. The maximum operating pressure in the LT1 cooling system is 15 psi for B/D-cars and 18 psi for F-cars, limited by a pressure cap. These limits are similar to other cars, but in the LT1, these maximum pressures are rarely reached. Running at a lower pressure drastically decreases the number of leaks and significantly improves overall reliability and durability.

Coolant Reservoir:

Corvette and B/D-car LT1 applications use a pressurized coolant recovery reservoir instead of a non-pressurized overflow tank used with conventional cooling systems. All of the coolant flows continuously through the pressurized reservoir, which is an integral part of the cooling system. The pressurized reservoir in the LT1 B/D-cars is connected to the cooling system in three places. One inlet hose connects to the top of the RH radiator tank, a second inlet hose is attached through a "tee" connection on the heater inlet hose, and a third outlet hose is connected to a "tee" connection in the throttle body heater outlet.

The pressurized reservoir is mounted at the highest point in the system, and provides a place where all air can be continuously scavenged from the coolant. Any steam and bubbles are allowed to rise to the surface, eliminating foam and providing pure liquid coolant back to the engine. Pure liquid coolant is returned to the system via the heater outlet hose connection. The pressure relief/vent cap in these systems is rated at 15 psi and is located on the reservoir rather than the radiator.

LT1 F-cars use a conventional coolant recovery system which consists of a non-pressurized coolant overflow tank connected to the radiator by a single hose. These cars use an 18 psi rated pressure relief/vent cap on the radiator like most conventional systems. Since these cars cannot scavenge air from the coolant as well as the B/D-car or Corvette systems, they have two air bleeder valves for manually bleeding trapped air from the system. One is in the thermostat housing, which is the same as all other LT1 engine vehicles, and the second one is located in a "tee" where the coolant from the throttle body connects to the heater return hose.

B/D-car LT1 (Caprice/Impala/Roadmaster/Fleetwood) Cooling Systems:

Standard equipment for all LT1 equipped B/D-cars is a dual electric fan setup with a 150-watt primary (RH) fan and a 100-watt secondary (LH) fan. The electric engine coolant fans are independently operated by the PCM (Powertrain Control Module) based on the inputs from the Engine Coolant Temperature (ECT) sensor, A/C Pressure Sensor, Vehicle Speed Sensor (VSS), and various other inputs.

The B/D-car coolant fans operate under PCM control at the following engine temperatures and A/C system pressures:

Fan Mode
Temperature A/C Pressure
Primary (RH) Fan ON 109 C 229 F 189 psi
Primary (RH) Fan OFF 105 C 221 F 150 psi
Secondary (LH) Fan ON 112 C 234 F 240 psi
Secondary (LH) Fan OFF 108 C 227 F 210 psi

Additionally, the PCM will turn off the
fans at higher vehicle speeds (above 48 MPH I believe) since running fans can
actually impede airflow through the radiator at high speed. Each fan also has a
minimum running time. Once activated, the primary fan will run for a minimum of
50 seconds, and the secondary fan for a minimum of 26 seconds. Finally, certain
Diagnostic Trouble Codes (DTCs) may cause the PCM to turn on one or both fans.

All LT1 B/D-cars have two transmission oil coolers and an engine oil cooler as standard equipment. The transmission coolers include a primary oil to water type inside the RH radiator tank, and a secondary external oil to air cooler (KD1) mounted in front of the radiator on the RH side. The external KD1 cooler is an aluminum stacked plate type cooler painted black with metal tube lines linking it in series with the other cooler in the radiator tank. LT1 B/D-cars also include an engine oil to water cooler (KC4) mounted in the LH radiator tank.

Optional B/D-car LT1 Cooling Systems:

There are two optional cooling system upgrades for LT1 B/D-cars, called V03 (Extra Capacity Cooling), and V08 (Heavy Duty Cooling). Performance models such as the WX3 (Impala SS) and 9C1 (Police) cars automatically get the upgraded V03 (Extra Capacity Cooling) system. V03 includes a larger radiator, an increased capacity A/C condenser, and an upgraded secondary electric fan. V03 is also optional on most B/D-car models.

Note that the '94 V03 (Extra Capacity Cooling) option uses a 150-watt primary (RH) fan, and an upgraded 240-watt secondary (LH) fan. In '95-'96 the V03 package was revised and no longer included an upgraded 240-watt secondary fan. Instead the standard 100-watt secondary fan was used, which is the same as the base cooling system.

B/D-cars other than the Impala SS or Police package Caprice also have an optional V08 (Heavy Duty Cooling) package which is part of the V92 (Trailer Towing) package. V08 includes the larger radiator, increased capacity A/C condenser, and upgraded secondary fan as in the V03 system, however it differs in the primary cooling fan. With V08 the 150-watt electric primary fan is replaced by a mechanical belt driven thermostatic clutch fan. To drive the mechanical fan, the V08 system includes a crank pulley, belt tensioner and bracket, and a large radiator shroud in addition to the mechanical fan itself. This package is not available on the WX3 (Impala SS) or 9C1 (Police) cars since the mechanical fan is driven by an additional pulley and belt on the engine crankshaft, which draws engine power thus reducing performance.

The mechanical fan used with the V08 cooling system contains a built-in thermostatic clutch which senses the temperature of air that has been drawn through the radiator. When the temperature of this air is below 66 degrees C (151 degrees F), the clutch freewheels and limits the fan speed to 800-1,400 rpm. When the temperature rises above 66 degrees C (151 degrees F), the clutch begins to engage, and the fan speed increases to about 2,200 rpm. The RH radiator hose in V08 equipped vehicles has a steel tube section near the fan designed to prevent damage in case of fan contact.

There are several SEO (Special Equipment Option) B-car ooling options which are included as standard only with 9C1 (Police) package Caprices. These include the following:

In addition to the standard inclusion of the V03 (Extra Capacity Cooling) package, all LT1 Caprice 9C1 (Police) cars also include SEO 1T1 (Silicone Radiator and Heater Hoses). SEO 1T1 consists of special green radiator and heater hoses made out of pure silicone rubber. These hoses are designed to last the life of the vehicle and never need replacement unlike the standard black rubber hoses. SEO 1T1 also includes heavy duty stainless steel worm gear hose clamps which replace the standard squeeze type hose clamps. The clamps have a solid full perimeter band, which prevents the hose from extruding between the slotted area where the screw fits. This also prevents the hose from being cut or damaged by the clamp, and allows a more even sealing force around the entire clamp perimeter.

The 9C1 Police package also includes SEO 7P8 (External Engine Oil to Air Cooler). This is an unpainted aluminum stacked plate type cooler which is mounted in front of the radiator on the LH side opposite the external transmission cooler. This heavy duty engine oil cooler replaces the standard engine oil to water cooler found in the LH radiator tank of other LT1 B-cars.

Also included with the Police package is SEO 7L9 (Power Steering Fluid Cooler). This consists of a loop of metal tubing installed between the radiator lower support and the front stabilizer bar. This cooler prevents the power steering fluid from overheating in rigorous driving situations such as high speed pursuit.

F-car LT1 (Camaro/Firebird) Cooling Systems:

Standard equipment for all LT1 F-cars with A/C is a dual electric fan setup with primary (LH) and secondary (RH) fans. There are two different wiring schemes used for these fans, an early design that was used in '93-'94 and a late design that has been used from mid-'94 up. Note that non-A/C F-cars have a single primary fan which operates at a fixed high speed.

In '93 and early '94 models with A/C, the two cooling fans are independently operated by the PCM (Powertrain Control Module) at a high fixed speed by using a single relay for each fan. Late '94 and newer F-car models operate both fans simultaneously in either a low or a high speed mode by using 3 relays. In low speed mode, the fans are powered in series. In high speed mode, the relays operate to power both fans in parallel, resulting in a higher speed of operation.

One way to tell which setup you have is by looking at the alternator. If an F-car is equipped with the 124 amp alternator (KG7), then the vehicle has the early design setup and the fans are operated independently. If the vehicle has the 140 amp alternator (KG9), then it also has the newer design configuration which operates the fans simultaneously in low or high speed modes.

The PCM operates the coolant fans based on input from the Engine Coolant Temperature (ECT) sensor, A/C Pressure Sensor, Vehicle Speed Sensor (VSS), and various other inputs. The F-car coolant fans operate at the following temperatures and pressures:

Fan Mode
Temperature A/C Pressure
Primary (LH) or Dual Low-speed Fan(s) ON: 108 C 226 F 248 psi*
Primary (LH) or Dual Low-speed Fan(s) OFF: 105 C 221 F 208 psi*
Secondary (RH) or Dual High-speed Fan(s) ON 113 C 235 F 248 psi
Secondary (RH) or Dual High-speed Fan(s) OFF: 110 C 230 F 208 ps

*Note - this information is probably incorrect, although it is quoted from the service manual.

Additionally, the PCM will turn off the fans at higher vehicle speeds (above 70 MPH I believe) since running fans can actually impede airflow through the radiator at high speed. Each fan or fan mode has a minimum running time. Once activated, the primary fan or dual low-speed fans will run for a minimum of 50 seconds, and the secondary or dual high-speed fans for a minimum of 30 seconds. Finally, certain Diagnostic Trouble Codes (DTCs) may cause the PCM to turn on one or both fans.

All LT1 F-cars with automatic transmissions also have a transmission oil cooler as standard equipment. The transmission cooler is an oil to water type mounted inside the RH radiator tank.

Optional F-car LT1 Cooling Systems:

There is only one option in an LT1 F-car with respect to cooling, and that is an engine oil cooler (KC4). The engine oil cooler is an oil to water design that is mounted in the LH radiator tank. The KC4 oil cooler is included with various other combinations of options on the F-cars.

Operating Characteristics and Observations:

I have an accurate digital temperature gauge installed in the RH cylinder head water jacket on my '94 Impala SS. I installed a brass "T" fitting in the RH cylinder head, in the tapped hole where the factory temperature gauge sender was originally installed. This allowed me to install both the original analog gauge sender as well as the sender for the new digital gauge. With the stock 180 degree thermostat, cruising at 80 mph on a cool night I would routinely measure coolant temperatures in the head as low as 167 degrees! If I slowed down, the temperature would climb up into the 170-180 degree range depending on ambient temperatures and cruising speed. The temperature would run in the 180s-190s cruising more slowly on a hot summer day. In heavy stop and go traffic, the temperature would quickly climb up into the 220-230 degree area, which is where the primary fan starts to come on.

Many have noticed as I have that the engine will actually run cooler in traffic with the A/C on. This is because turning on the A/C will also cause the PCM to activate at least the primary fan, and possibly the secondary fan (depending on A/C system pressure) as well.

The radiator and A/C condenser in B/D-cars equipped with the RPO (Regular Production Option) V08 (Heavy Duty Cooling) or V03 (Extra Capacity Cooling) systems are extremely large, perhaps the largest of any passenger car on the market today. The cooling and A/C system performance on these cars are outstanding, in fact the best I have seen on any vehicle.

Recommendations for Cooling System improvements:

If you have a B/D-car, there are several easy improvements you can make by simply adding the cooling related SEOs (Special Equipment Options) from the 9C1 Caprice Police package. For example, I have installed all of the Police package cooling upgrades in my '94 Impala SS. This includes the 1T1 silicone hoses, 7L9 power steering fluid cooler, and 7P8 external engine oil cooler. Combined with the already powerful V03 cooling system, these factory upgrades combine to form the most extreme duty factory cooling system present on any automobile I have seen.

If you have an F-car which was not factory equipped with the optional KC4 engine oil cooler, then I would highly recommend installing it as an upgrade. The KC4 option consists of a different radiator with the engine oil cooler located inside the LH tank. An adapter installs on the oil filter pad between the filter and the engine, and lines run to the cooler in the radiator tank.

There are two other cooling system improvements that can be applied to any vehicles with the LT1 engine, including the Corvette and F-cars (Camaro/Firebird). These are to change to a colder 160 degree thermostat (180 is standard), and to alter the electric cooling fans to come on at a lower temperature. This latter function can be accomplished by adding an external thermostatic switch to the fan circuit, or by re-programming the PCM fan operation settings.

Bypass Throttle Body:

You can bypass the throttle body for a cooler (denser) air charge (and more power), but the line from the steam vents *must* be connected to the reservoir, and the reservoir to the heater hoses as well. Without the steam vents you will have steam pockets and trapped air building up in the heads, which will cause spot overheating. This will result in blown headgaskets and other problems.

Fan Activation:

As mentioned earlier in this article, the stock fans do not come on until at least 225 degrees, which I feel is too hot. To prevent the engine from heating up this high in traffic or while moving slowly, I installed a 203 degree GM thermostatic switch (p/n 3053190) in a pre-existing tapped hole in the LH cylinder head water jacket, and wired it to both the primary and secondary fan relay via a 3-position toggle switch.

When the coolant temperature reaches 203 degrees, the primary or secondary fan (depending on the setting of the toggle switch) will run. This prevents the engine from running hotter than about 200 degrees or so. I have tested this modification in 100 degree ambient temperatures, while trapped in stop and go traffic, and never saw coolant temperatures higher than 205 degrees. I wired the toggle switch to operate either the primary or secondary fan, as well as to disconnect the thermostatic switch from the circuit, thus disabling this function. No matter what the toggle switch setting, the PCM still has control over the fan relays, and will continue to operate the fans oblivious to the additional thermostatic switch function.

As an alternative to the GM switch, I have found a company that makes higher quality switches in a variety of temperature settings that work as a direct replacement for the GM switch:

John Flagg
GMP Parts Company
9901 Kent Street Suite #2
Elk Grove, CA 95624
(916) 685-1055
(916) 685-3139 FAX

GMP has the highest quality switches available in a number of different temperature ranges so you can pick whatever temp you want the fans to go on. I don't recommend going lower than 185 degrees on the switch with a 160 degree thermostat or the fans will likely remain on all the time. This is because normal engine operating temperature is up to 20 degrees or more higher than the engine thermostat setting.

I have more recently purchased the Hypertech Power Programmer, which re-programs the PCM to turn the primary fan on at 176 degrees (instead of 225), and the secondary fan on at 191 (instead of 232). At first I installed the Hypertech program without the recommended 160 degree thermostat in order to observe the operation of the fans. I found that the primary fan would run continuously once the engine had warmed up, and even the secondary fan would be on most of the time. This is due to the overlap between the high thermostat setting and the lower fan activation temperatures programmed in by Hypertech. The new settings were turning the primary fan on at a setting lower than the thermostat itself would open.

Another alternative over the Hypertech device is to simply have your PCM reprogrammed by a service such as that offered by my friend Ed Wright at Fastchip . He can not only reprogram your fans, but can also optimize many other areas of the PCM programming, adding power and driveability. Tell Ed I sent you if you call. Reprogramming by offers much more in the way of customization than using the fixed calibrations in the Power Programmer.

After installing the recommended 160 degree thermostat, the fans worked normally, and would only begin to run after the car was not moving which allowed the temperature to rise. In actual operation I saw temperatures while moving about 10 degrees lower than what I observed with the 180 degree thermostat. While moving very slowly or sitting stationery, the engine would never climb above the low 190 range, no matter how high the ambient temperatures was or how slow I was moving. After observing this operation, I would wholeheartedly recommend the 160 degree thermostat and the Hypertech Power Programmer. If you use the Power Programmer, then the 160 degree thermostat MUST be installed or the fans will run continuously, which is not good for either the fans, alternator, or battery.

If you do not want to purchase the (fairly expensive) Power Programmer, then I highly recommend installing the 203 degree thermostatic fan switch I listed, which will prevent the excessive temperatures encountered in traffic that are allowed by the stock PCM program settings. The fan switch will work well with either the stock 180 degree thermostat or a 160 degree unit, and will limit the maximum coolant temperatures to 205 degrees or less.



vader wrote:http://temp.corvetteforum.net/c4/vader86/




This page is in response to the numerous threads on temperature operating ranges and overheating complaints that comes up EVERY year on the forum starting in May. Since the Mods won't give us a sticky on it, I decided to write this up to save time writing it in each post.

Normal operating ranges,
Oil-anywhere between 210-230
Coolant-should settle at about 15-20F below the oil temperature

LT1 cars will run just a bit warmer than L98s, but the same ranges apply.

Main fan on/off:
Varies just a bit in exact temperature over the years, but it should come on anywhere between 225-228F (coolant), I say that because the in-car gauge is rarely so accurate for you to say its coming on exactly when the manual says it should.
The main fan will also cycle with the A/C running.
Aux fan (if you have it)-in front of your radiator and condensor, and it should come on just above your main fan temperature, say 228F, though in 85-86 it came on at 238F.

Stock Thermostats-
L98-195F (coolant)
LT1-180F (coolant)

Once the engine starts, your car will proceed upwards to the thermostat opening temperature, at which point it should hold steady as the stat cycles open and closed. At that time, the oil temperature will catch up with the coolant and usually passes it. This drags the coolant temp up towards the fan setting. Generally it'll settle at about 15-20F difference between the two.

Danger zone-if you have aluminum heads, do NOT allow the coolant to reach 250-260+, or you're risking a head gasket. That applies to both engines. A dino oil engine can handle oil temps ~250 for short durations, but above this the oil breaks down and you need to change it sooner than usual. Synthetics can withstand ~300F.

Things to do if you suspect the engine is overheating:

1.Check to see if the thermostat is indeed working. Car temperature should stabilize momentarily at the thermostat opening temperature. If it doesnt, replace it.

2. Check to see if the fans are working. Let the car idle up to fan temperature and make sure they come on when they should. Try running the A/C to see the fan itself actually works at all, it should come on within a few minutes of running. Main fan relay is on the radiator shroud starting in '88, and earlier years have it just below the Master Cylinder on the wheel-well.

3. Check to make sure the WP is not weeping. There are weepholes in the WP that will leak when its bad. Its hard to diagnose otherwise.

4. Remove air bubbles in the system, and check for pressure leaks. Old caps lose pressure and should be replaced every 2-3 years when you should flush your system. Also check for small leaks in the hose between radiator and overflow/surge tank and make sure all hoses are tightly clamped. Some leaks dont happen until the engine is hot, you must be sure.

To burp the motor-for the L98 let the engine warm up with the rad. cap off, until the thermostat is open fully. While you are doing this, hold the engine at 2000rpm or the coolant will just bubble out. You can do it by yourself, but its best to have another person inside the car. Once the stat is open and the throttle is pressed, the coolant level will drop....fill it up and replace the cap. It may take 2 tries to get all of the air out. LT1 systems use a bleed screw next to the TB to allow air to escape.

5. Clean the space between radiator and condensor. The C4 is a vacuum cleaner and sucks things up through the nose, because the intake actually breathes in air after its passed through the radiator and condensor (not through the little air gaps in the hood or shroud). Debris passes above the condensor and settles in the space between it and the radiator. Once this is clogged the temps will end up about 10-15F higher. Dirt and grime will also cling to the fins in the radiator, and must be removed.

See the Techtip on doing this, you must remove the shroud (not as hard as it looks) to suck the debris out with a shop-vac. You should also remove the radiator and use a screwdriver to clean out the fins and straighten each one before putting it back in.

6. Flush the system-old coolant becomes acidic and eats away at rubber internals and the radiator itself, causing leaks to form. You should flush the system once every 2-3 years and replace with 50/50 coolant/distilled water mixture. You MUST use distilled water, regular tap has some of those acidic/ionic impurities aforementioned.



Does the car still overheat?:
If you see any plumes of white smoke in normal operation, once the car is hot (ignore any light wisps of smoke on startup, it may just be condensation in the exhaust, especially when it gets cold at night), then you have a head gasket failure. If it doesnt do that and still continues to rise, then theres either a pressure leak in the system that you havent found or it could still be a head gasket. It doesnt have to look like a shuttle launch, but usually it does.

If the car is just running too hot for your tastes the only permanent fixes are a combination of the following,

1. Reset the fan temperature in the ECM, either from a chip or laptop tune for PCM modules. 195-210 should be fine.

2. Change the thermostat to a lower temperature, this applies more to L98s than LT1s in my opinion. I use a 160, and theres another discussion of that whole debate on another page here.

3. Add a larger radiator. DeWitts, Griffin, BeCool, Davis, etc. These will not help idle temperatures so much, but once you get moving the temps drop fast. I now see a 30F difference between oil and coolant with the DeWitts on the highway, even on hot days it keeps the coolant low (mine was 180F in 100F outside heat at 70mph on the highway).

4. Better water pump-Stewart, FlowKooler, etc. These affect idle temperature rises more than anything else, since they pull coolant in and push it out faster than the stock pump at idle. The car will still proceed upwards in temperature t idle, but a bit slower.

I have done all 4 in that order to my car, and the first 2 fixed the problem.
IF YOU CAN,T SMOKE THE TIRES AT WILL,FROM A 60 MPH ROLLING START YOUR ENGINE NEEDS MORE WORK!!"!
IF YOU CAN , YOU NEED BETTER TIRES AND YOUR SUSPENSION NEEDS MORE WORK!!
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Re: cooling off that c4 corvette

Postby grumpyvette » December 6th, 2011, 12:52 pm

Cooling System Operation and Testing


Electric cooling fans attached to the radiator keep the LT1 from overheating when there is little or no air passing through the radiator core (car going very slow or stopped and engine running). It is normal for the temps on the gauge to go up to the middle or past middle of the gauge before the fans kick on. The middle of the gauge is in the range of 210º - 220º. With factory programming, the PCM will command low speed fans (or primary fan) "ON" at 226º and "OFF" at 221º and high speed fans (or secondary fan) "ON" at 235º and "OFF" at 230º. The fans should come on before it gets to any part of the red zone. (see "dual fan configuration" below about primary and secondary fans)
The f-body LT1 uses a 180° thermostat as stock. Crusing temps are generally 10°-20° higher than the thermostat rating.

The PCM gets it's temp readings from a sensor that is in the water pump. If the reading the PCM receives is inaccurate, the fans may not come on at the correct time. The PCM also uses this temperature for lookup in calculation tables. If there is a problem that causes the reading to be always low (cold), the PCM will add extra fuel. This can cause hard starting when warm and an overly rich condition when running.

The gauge gets it's information from a sensor that is in the driver's side head. Inaccurate gauge readings can be from this sensor or it's wiring (the wire burned on a header pipe is common). The temp that the PCM sees can be monitored with a scan tool and compared to the gauge reading. They should be close, but don't expect them to be "perfectly" synchronized.

The fans are programmed to come on when the a/c is turned on. A/c Pressure monitoring sensors feed the PCM info and depending on the situation, the PCM may command the fans off for brief periods. Also, when the car reaches sustained higher speeds, the fans may be commanded off so incoming air can flow through the radiator unimpeded and provide the cooling needed.

Fans will also come on when the SES lamp comes on. The PCM does this when certain (most) DTCs are detected to protect the engine from a situation where it may overheat.


There are two versions of the dual fan configuration:

1993-1994 - Primary and Secondary fans that operate at only one speed. When initially commanded on, only the primary fan (driver side) comes on. It operates alone at full speed. If the temp threshold is met for addtional cooling, the secondary fan (passenger side) also is commanded on. At this point, both fans are running at full speed.
These fans use a two relay architecture that can be seen in the fuse/relay panel that is under the hood.

In late 1994 and into 1995, there was a change to low and high speed fans. When initially commanded on, both fans will come on at a low speed. When the high speed temp threshold is met, they both bump up to high speed. A three relay architecture is used for this fan version (seen in the fuse/relay panel). By adding a third relay, low speed can be achieved by running the power to the fans in series. This way, each fan does not get full voltage and runs at a slower speed. High speed happens when the relays switch to provide full voltage to both fans. Low speed is less noisy and should result in greater fan longevity. High speed is not always needed.
IF YOU CAN,T SMOKE THE TIRES AT WILL,FROM A 60 MPH ROLLING START YOUR ENGINE NEEDS MORE WORK!!"!
IF YOU CAN , YOU NEED BETTER TIRES AND YOUR SUSPENSION NEEDS MORE WORK!!
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Re: cooling off that c4 corvette

Postby grumpyvette » December 6th, 2011, 12:53 pm

Here are some fairly simple things to check for various complaints:

~Fans are not operational at any time~


Check fan fuses in the underhood fuse/relay panel
Check fan relays (same location). Aside from getting out any electrical equipment to test the relay, you can swap it with another one (such as the fog lamp relay) and test for function. See if the relay works for the fog lamps and/or the swapped-in relay makes your fans work. Nearly all the relays in the panel are the same, except for maybe the ABS relay.
You can jumper two pins on the DLC that should cause the fans to come on. 1993-1994 cars with the 12 pin DLC can jumper pins A and B. On a 1993, that is the same way that you would retrieve trouble codes from the ecm. The 1994 won't give you any codes, but the fans will engage. 1995-1997 uses pins 5 and 6 on the 16 pin DLC to initiate what is called "field service enable mode". That will cause the fans to come on and operate most sensors for sanity checking. After placing the jumper on the correct pins, turn the key to ON (don't start). If the fans work after jumpering the DLC, your PCM is capable of operating the fans and all fan wiring/relays should be ok.
Deeper problems can be solved through testing and using the wiring schematic.


~Fans don't come on except when the a/c or SES is on~

~Temp gauge continues to rise with no automatic fan operation~


With a scan tool, check to see what temp the PCM is seeing from the sensor in the water pump. Make sure you are aware of the temps the fans come on (stated in the beginning of this article). If the temp it sees is incorrectly low, it won't know to turn the fans on. Another possibility is that the temp is really ok, but the gauge is reading wrong. That is why you need to use the scan tool to see and compare the readings. Info on testing wiring and sensor can be found here.
If that looks ok, then your PCM may have issues. You could always try resetting the PCM by pulling the PCM BAT fuse for about 30 seconds.


Other cooling issues

~Temps escalate with speed and fans are working~


Check for obstructions/debris in front of the a/c condensor (sometimes even between the condensor and radiator).
Make sure the air dam is on. Cars with low ground effects may need a special air dam to scoop up enough air for cooling.
Check the thermostat for proper operation. It can be tested in a pan of water, heated on a stove. It should begin to open at it's rated temperature and then open fully as it gets warmer.
While on the subject of thermostats, the LT1 reverse flow system uses a special, long thermostat that works together with the passages in the water pump to provide proper coolant routing. If you use an old SBC style thermostat, you run the risk of the system not operating with proper efficiency and it may overheat. Escalating temps can be caused by poor air or coolant flow.


~Generally running hot~


Examine system for any of the items mentioned above.
Check for air in the cooling system via the air bleed screws.
Check or replace the radiator cap (especially if you have heard lots of gurgling and overflow into the remote reservoir. The F-body system uses an 18 psi cap.
Check for any obvious leaks. If needed, rent a pressure tester that will allow you to pressurize the system while it is cool. This will allow you to see if it holds pressure and look for any leaks.


~Low coolant lamp on~


The low coolant sensor is a most common cause of complaint. If it gets dirty, it may cause the lamp to come on when the coolant level is actually ok. Sometimes it fails and no amount of cleaning will fix it. The sensor is only connected to the lamp on the dash. It does not report to the PCM and no DTC's will be set. Because of this, some people choose to simply unplug the sensor to get rid of the annoyance without having to fix it. Unplugging it will make the lamp go out, but you will have to monitor the coolant level yourself. As critical as the coolant is to the LT1, having it working makes sense.

If the light seems to come and go, make sure the level in the remote reservoir is proper. Normal operation of the cooling system often causes coolant from the radiator to overflow into the remote reservoir. As the engine cools down, the radiator creates a vacuum and pulls this coolant back into the radiator. The piping from the neck of the radiator to the reservoir must be air tight for this to occur. Since these cars are getting older, it is not uncommon to get a small leak in the pipe that goes under the battery. Acid wears away at the pipe until it makes a hole. Even a small hole is enough to cause problems. A telltale sign is a small amount of coolant under the right front of the car after it is parked a while. Usually, only taking out the battery will reveal where it is coming from, because it slowly drips on the splash panel underneath and may travel along to another area to drip off.

If the lamp is coming on for no apparent reason (you have verified coolant level is fine-that is, checked the level in a cold radiator and verified you have the proper level in the remote reservoir), you have a few choices:
Clean the sensor and try it again
Replace the sensor
Unplug the sensor (the low coolant lamp will stay off and there will be no monitoring of the coolant level)


Thermostats and cooling

The temp rating of the thermostat is merely at what temp it will begin to open and allow coolant flow. It is purely a mechanical, temperature reactive device and has no external control or monitoring. A frequent reason behind a lower temp thermostat is to be able to make use of more aggressive spark advance without the engine having any spark knock (detonation or pinging). Excessive spark knock is detrimental to the engine. Spark knock is also monitored by the computer and timing advance is pulled (retarded) by the computer. When timing is retarded, performance and power will decline.

There is a fine line between between enough spark advance for high performance and the penalties for too much. The engine temperature plays a role in that the coolant wicks away heat from the combustion chambers in the head. Higher overall engine temperature results in higher overal combustion chamber temperatures. Installing a lower temperature thermostat alone may actually decrease performance because a certain amount of heat is needed to burn the air/fuel mixture efficiently. If you see a decrease in gas mileage with a lower thermostat, alone, this may be the reason. The trick is to lower the temperatures but add enough timing to increase performance over what it was originally.

An often asked question is "Will my engine stay cooler with just a 160° thermostat?". The answer is yes, as long as there is good air flow across the radiator and the cooling system is working efficiently. Note that engine temps will still climb as they did before when you are stopped (as in traffic). However they may not rise as high, since you are starting out at a lower temperature than before. When you are moving again, it will be possible for the temps to lower more than what the 180° thermostat would previously allow. Cruising down the road, your engine should definitely stay cooler than before. Remember that the rated temperature of a thermostat is the temperature that it begins to open. While crusing on a moderate temperature day, an LT1 will generally run 10°-20° warmer than the thermostat temp rating. Make sure you use the correct, long LT1 thermostat (not an SBC thermostat) as described in the troubleshooting section above.

The thermostat only has control of opening temp to allow coolant flow, after that it does nothing but cause a predetermined amount of restriction in the flow. To make the most of the lower temperature thermostat, it should be accompanied by reprogramming of the fans, so that they will come on at a lower temperature. This will help to maintain a lower overall temperature in all driving conditions (especially when stopped in traffic). It is not mandatory that you do this and a 160º can be installed by itself with no other modification.

Something else to consider is that when the engine gets to ~220º (even before the stock fan ON temp of~226º) and you are at MAP loads of 70Kpa or more, the PCM begins to retard the timing. That is one reason why people feel their cars don't run well when they are hot. The GM folks built the retard into the spark tables because when the engine is hotter, there is more chance for spark knock. If you can keep the temperatures from getting up into that range, then you might feel more power when you need it.

Altering the fan ON temps can be done through reprogramming the computer or an aftermarket "fan switch" such as sold by SLP and JET . Manual fan switches can also be wired up to operate the fan relays so that the fans can be operated at any given time the driver wants (like in staging lanes). There are explanations on how to wire the manual switch up on the 'net and there are even a couple of wiring diagrams in the electrical section of my Tech Page. If you look at the fan schematics, you can probably see that there can be several solutions to operating the fans manually (my preference being to control the existing relays).

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I upgraded to a 200 amp rated alternator on my 1985 corvette, I also per the instructions that came with the alternator,upgraded the cable gauge too a serious GAUGE copper connection cable, I ran a new 2 ga from the alternator output stud
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http://www.dbelectrical.com/casearch.as ... ageSize=60

http://www.dbelectrical.com/p-9594-alte ... -1993.aspx

http://www.dbelectrical.com/p-3478-ford ... t-101.aspx
http://www.madelectrical.com/electrical ... ire3.shtml

http://www.madelectrical.com/electrical ... remy.shtml

viewtopic.php?f=70&t=2133&p=5744#p5744

http://www.summitracing.com/parts/bss-c ... dia/images

the NEW REQUIRED UPGRADE, 4 ga wire used to charge the battery on a 160-200 amp alternator used to upgrade from a stock 70-90 amp alternator should run between the alternator power out directly to the battery positive, 4 ga is not heavy enough to run from the battery positive terminal to the starter

95blklt1
posted this bit of info

HERES a Dewitt aluminum rad and wow is it a lot thicker! Here is the old:
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And the new:
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it should be obvious the DEWITT ALUMINUM radiator provides far more heat transfer surface area, Theres several well known sources for quality aluminum radiators and just as obviously theres clearance and space issues to consider.
most big blocks used in engine swaps produce a good deal more power than a stock SBC and burn a good deal more fuel, this results in a good deal more heat thats generated that needs to be transferred efficiently to outside air flow,the engines power generating extra power seems to always require a larger size radiator , now obviously without knowing the radiators fluid capacity,surface area and air and coolant flow rates I can,t tell if your radiator is fully up to the task at hand, but the symptoms that are usually described, of the engine heat building rapidly if the cars not moving tend to point to a need for a higher air flow rate thru the radiator.
I generally use 3 core 1.5 inch tube designs , but theres a good many factors involved, and adding a 200 amp alternator or a more efficient fan and adding an additional oil or trans cooler could very easily make a huge difference, as it lowers the heat loads on the cooling system



directly to the battery positive terminal ,then ran an extra 2 ga ground from the battery neg to the cars frame and a new ground ribbon cable
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between the frame and engine block.
the result was far more than anticipated, the engine ran smoother at all rpm level, the cooling fans ran noticeable faster at idle and the engine ran cooler, the ignition spark also seemed to be stronger and brighter and the electrical arc,s snap sound louder when you pulled a plug wire off a plug to test spark on an idling engine


http://www.summitracing.com/parts/SUM-G1198/?rtype=10

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http://www.powermastermotorsports.com/f ... ators.html

http://www.dbelectrical.com/p-3478-ford ... t-101.aspx

http://www.dbelectrical.com/p-4416-new- ... -11se.aspx
IF YOU CAN,T SMOKE THE TIRES AT WILL,FROM A 60 MPH ROLLING START YOUR ENGINE NEEDS MORE WORK!!"!
IF YOU CAN , YOU NEED BETTER TIRES AND YOUR SUSPENSION NEEDS MORE WORK!!
grumpyvette

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Re: cooling off that c4 corvette

Postby grumpyvette » July 2nd, 2012, 2:13 pm

IF YOU CAN,T SMOKE THE TIRES AT WILL,FROM A 60 MPH ROLLING START YOUR ENGINE NEEDS MORE WORK!!"!
IF YOU CAN , YOU NEED BETTER TIRES AND YOUR SUSPENSION NEEDS MORE WORK!!
grumpyvette

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Re: cooling off that c4 corvette

Postby grumpyvette » August 9th, 2012, 2:59 pm

HOOKEDONVETTES POSTED THIS INFO

Manually spin the fan blade of the fan that doesn't work to
verify the fan motor isn't seized.

The fans use 3 relays mounted on the driver side
on the end of the radiator.

Primary cooling fan is an the driver side.
Secondary cooling fan is on the passenger side.

There are two modes of fan operation.
Both fans at half speed. 6 volts
Both fans at high speed. 12 volts.

There are two control lines the PCM grounds to
enable the fans.

PCM grounds the Dark Green wire for low speed.
Relay #1 is energized.

PCM grounds both the Dark Green wire and a Dark Blue
wire for high speed.
All three relays #1, #2 and #3 are energized.

Three fuses protect the circuits.
Fan fuse 5 amp located on passenger side of the dash.
This must be good because you say one fan does run.

Primary coolant fan 30 amp Maxifuse located under the hood.
Must be good if the driver side fan works.

Secondary coolant fan 40 amp Maxifuse located under the hood.

You can identify the relays by the color of the wires that
go to the relay sockets.

Relay #1 has the following colored wires.
Pink, Dark Green, Red and a Light blue wire.

Relay #2
Pink, Dark Blue, White and 2 Black wires.

Relay #3
Pink, Dark Blue, Red and a White wire.

To test the fans turn the ignition On.

Manually ground the control lines. Stick a nail
or probe, jumper wire etc... into the bottom of
the relay socket and ground the Dark Green wire.

Both fans should run at low speed.

Ground the Dark Green wire and the Dark Blue
wire and both fans should run at high speed.

Another method you can use is to carefully pry/remove
the plastic cover off of the relays. You can then
manually energize the relays by pushing down
on the metal plate.

Push down on the plate on #1 relay and both fans
should run at slow speed.

Push down the metal plate on all relays and both
fans should run at high speed.

Image

Image
Image
The relays are all the same so you can swap them around.
IF YOU CAN,T SMOKE THE TIRES AT WILL,FROM A 60 MPH ROLLING START YOUR ENGINE NEEDS MORE WORK!!"!
IF YOU CAN , YOU NEED BETTER TIRES AND YOUR SUSPENSION NEEDS MORE WORK!!
grumpyvette

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Posts: 14105
Joined: September 14th, 2008, 1:40 pm
Location: florida

Re: cooling off that c4 corvette

Postby grumpyvette » November 9th, 2012, 6:16 pm

HERES A BIT OF USEFUL INFO


"P 1641, P1642, codes in my 96.
hi,GRUMPY>

yesterday i pulled some codes and they turned to be for the fan relays,

the service manual test procedure use a scan tool to give an on and off command to the relay, i think that was a tech 1 scan tool.,

i dont have tech 1 or 2 either, but i have the auto xray scanner. which does not support this feature.

so any one knows an alternative way to complete the test prosedure without using the tech 1?

any other tool can do it?

this problem occurred when i changed the internal under dash harness is it possible that the harness is faulty (used one).??
thanks "


NEVER MIND
I fixed the problem,after some research I found a loose electrical harness connector

the codes are off now. the problem was with the connection between the I/P harness and the front body harness. it is located behind the battery.



the pins was covered with grease, thus it wasnt connected well.
i clean it and now it is ok.

http://www.dbelectrical.com/casearch.as ... ageSize=60

http://www.dbelectrical.com/p-9594-alte ... -1993.aspx

http://www.dbelectrical.com/p-3478-ford ... t-101.aspx

http://www.autozone.com/autozone/repair ... 528008fd94

http://www.autozone.com/autozone/repair ... 528008fd94



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IF YOU CAN,T SMOKE THE TIRES AT WILL,FROM A 60 MPH ROLLING START YOUR ENGINE NEEDS MORE WORK!!"!
IF YOU CAN , YOU NEED BETTER TIRES AND YOUR SUSPENSION NEEDS MORE WORK!!
grumpyvette

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Site Admin
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Posts: 14105
Joined: September 14th, 2008, 1:40 pm
Location: florida

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