leak down test



leak down test

Postby grumpyvette » October 3rd, 2008, 8:30 am

first DON,T PAY FOR IT ...DO IT YOURSELF!!!
IT WILL COST LESS EVEN AFTER PAYING FOR THE TOOLS AT MOST GARAGES.

youll find that youll gain basic skills, own new tools and PAY LESS MONEY[/b] :

When testing EACH CYLINDER,with the leak down test gauge make sure the adapters firmly seated and a bit of oil on the threads won,t hurt either, try and find a quiet and well lit place to test, and do a vacuum test also
viewtopic.php?f=62&t=882&p=1390&hilit=propane+leaks#p1390
during the leak-down testing procedure,Listen at the intake manifold for intake valve leakage.
during the leak-down testing procedure,Listen at the exhaust manifold for exhaust valve leakage
during the leak-down testing procedure,Listen at the valve covers or oil fill cap for ring leakage--you'll always have some, but its usually not huge on an engine in good shape, retest after squirting a bit of oil into the cylinder on each cylinder,does it change the reading or sound?.
if your experiencing high rates of crank case pressure chances are good its the result of pressurized gases getting past the ring to bore seal at some point in the pistons travel
during the leak-down testing procedure,Listen and visually check for bubble in the radiator coolant, at the radiator cap for air leakage into the cooling system.
http://www.goodson.com/Dual-Gauge-Leak-Down-Tester/

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ANY leakage into the exhaust, intake, or radiator is cause for concern.

[b]
read these links 90% of the info you needs in the links

LOOK FOR LOOSE OR CORRODED ELECTRICAL WIRING CONNECTORS, in THE WIRING HARNESS, and VERIFY YOUR FIRING ORDER, YEAH I KNOW YOUR SURE ITS CORRECT, CHECK IT CAREFULLY AGAIN, YOUR NOID TEST LIGHT AND MULTI- METER CAN SAVE YOU A GREAT DEAL OF PROBLEMS AND SCRATCHING YOUR HEAD IF YOU TEST BASIC ELECTRICAL CONNECTIONS< RESISTANCE AND VOLTAGE, CHECK YOUR SENSORS AND GROUNDS, A SHOP MANUALS MANDATORY, HEAT SENSORS AND IGNITION MODULES AND OIL PRESSURE SENSORS HAVE A LONG TRACK RECORD OF FAILING OR PARTIALLY AND INTERMITTENTLY NOT FUNCTIONING
http://www.carcraft.com/techarticles/116_0406_cylinder_leakdown_tester/index.html

http://www.nichols.nu/tip420.htm

http://www.hotrod.com/techarticles/engi ... rs_tested/

http://www.globaltoolsupply.com/cgi-local/SoftCart.exe/online-store/scstore/p-P1-275.html?E+scstore

http://www.tavia.com/cat8.html#3

http://vmaxoutlaw.com/tech/leakdown_tester.htm

http://www.motorcycleproject.com/motorcycle/text/leakdown.html

http://www.summitracing.com/parts/pro-66839/overview/

http://www.summitracing.com/parts/otc-5609/overview/
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http://goodvibesracing.com/Leakdown%20Tester.htm
1) For most accurate results, engine should be up to operating temperture.

2) Remove all spark plugs.

3) Rotate crankshaft until piston being tested is at top dead center of compression stroke.

4) Screw the spark plug adaptor hose into spark plug hole making the sure the o-ring is seated properly.

5) Connect the spark plug adaptor hose to the coupler of the leakdown tester.

6) Connect leakdown tester to a good source of compressed air, preferably a filtered and water trapped source.

7) Adjust the regulator on the leakdown tester so the the LEFT HAND GAUGE indicates at least 10 pounds less than your sorce pressure. The leakdown percentage conversion table shown below is based on regulated pressures of 100, 90, or 75 psi.

8) Read the RIGHT HAND GAUGE (differential gauge), then look up gauge reading on the conversion table below to get actual leakdown percentage. After noting percentage of leakage, turn the regulator knob counter-clockwise to relieve the pressure. This reduces the shock to the gauges. If you ever get an unrealistically low pressure reading on the right hand gauge, there is a finite possibilty that something is blocking the small orfice located within the hex tube located between the regulator and the main body of the leakdown tester.

9)To remove any obstruction that may be lodged in the metering orfice, unscrew the hose coupling assembly from the aluminum body. Ultilizing a 1" wrench, remove the knob assembly from the regulator. Blow compressed air in the opposite direction (from the coupling end) to clear the orfice. Re-assemble the regulator and the coupling.

NOTE: DO NOT ATTEMPT TO REMOVE THE BRASS HEX NIPPLE BETWEEN THE REGULATOR AND THE ALUMINUM BODY. DAMAGE MAY RESULT.

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when the test is done correctly results normally fall in the 2%-15% range and if testing shows 35% -100% its usually indicating a broken ring, burnt valve, bad head gasket, or a detonation damaged piston,etc. now if the piston was not at tdc, or a valve might be badly adjusted because the guy didn,t bother to lock the engines rotation durring the testing or remove the rocker tension, results are going to be suspect.
heating the engine up by running it prior to testing seems to help the test results slightly but it makes working on the engine durring testing a huge P.I.T.A. so its rarely done.
squirting some 20w50 oil into a cylinder than retesting will generally give you some indication of the leaks source if the results change because oil will tend to seal rings boosting results but not valves
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: leak down test

Postby grumpyvette » April 6th, 2009, 6:18 pm

this is also a good inspection tool
GOOGLE PV-618 and PV-636

ProVision 618 Flexible Fiberscope w/ 18" Non-Obedient Shaft and slightly less than 1/4" diam, cable for easy access

http://www.thetoolwarehouse.net/p-6283- ... pv618.aspx
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http://www.amazon.com/Vision-Flexible-B ... B000BHO28S

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High resolution lens provides a clear image of objects as close as 3/4 inch and over one foot away while providing a wide 40 degree field of view.
Powerful lamp illuminates dark crevices on-demand with the push of a button conveniently located on the handle.
Ergonomically designed handle is comfortable to hold and allows one-handed focusing and light activation.
Rugged and water resistant, ProVision is made of high impact ABS and flexible cable sheathing. (Note: Shaft is water resistant, not the handle.)
PV-618 and PV-636 models have .23” diameter, flexible, non-obedient cable. Durable carrying case included.
Accessories available to optimize ProVision for specialized applications.
Made in the USA
Specifications:

Cable Length: 18" (457.2mm)
Cable Diameter: .23"
Handle Length: 6" (152.4mm)
Handle Width: 1.43" (36.2mm)Overall Length: 24" (609.6mm)
Weight of Scope w/ Carrying Case: 1 lb. 5.7 oz (615 g)
Field of View: 40°
Optimal Viewing Distance: Min. .8" (20mm); Max. is dependent upon ambient lighting conditions.
Lamp Volts: 2.7 volts (Halogen)
Power Source: 2 AA batteries (not included)
Pressure Necessary to Operate Lamp: 2.9 avg. p/psi; 3.2 max. p/psi


drain your oil and look at the cam thru the oil pan drain hole, or pull a spark plug and inspect the valve or piston condition
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: leak down test

Postby grumpyvette » June 30th, 2011, 8:16 am

540 RAT posted this good info

Using a compression tester to check the basic condition of an engine is better than nothing, but it is NOT the best choice. Compression test results can be inaccurate and inconsistent. This is because the condition of the battery, variations in ambient temperature, and the effects of the presence or lack of oil (if the engine has been sitting) around the rings which helps seal them, can all affect the results. This makes a compression test only a mediocre test at best.

Leakdown testing is by far the best method for checking an engines basic condition. It is done by checking each cylinder at TDC of the compression stroke. And any leakage heard, helps to pinpoint where any problems are located. Air leaking out of the carb indicates a leaking intake valve. Air leaking out of the exhaust system indicates a leaking exhaust valve. Air leaking out of a breather indicates ring leakage. And air leaking out of the radiator cap opening indicates a leaking head gasket.

I've tested the 3 different types of leakdown testers.

One is a single gauge tester that reads leakdown percentage directly. This one is NOT recommended because its accuracy is typically not the best.

Another one is a dual gauge low input pressure (typically around 35 psi or less, depending on the particular unit) type that has one psi gauge and one gauge face that shows leakdown percentage directly. These are usually fairly inexpensive, and are also NOT recommended because of their typical inaccuracy.

And the last type is a matching dual psi gauge high input pressure (usually can go up to 100 psi) type. This type is convenient to use, and has good accuracy, making it clearly the best of the 3 leakdown tester types. So, if you decide to get a leakdown tester, do yourself a favor and get this type.

Note: Input pressure can be referred to in two ways, static and dynamic. Static means you set the regulator to the desired input pressure, say 80 psi (more on that below) with the tester NOT connected to the engine yet.

Then once you do connect the tester to the engine, the pressure will drop somewhat, becoming dynamic input pressure. You can then readjust the regulator to bring that dynamic input pressure back up to the original 80 psi, if you want. But I've found no difference at all in the final leakdown percentage results between doing that, or just letting the pressure drop somewhat and leaving it there. So, the most convenient method is to simply set the static input pressure to 80 psi and simply leave it.

The way to get to the final answer for a given test is:

For example, after you connect the 80 psi static pressurized tester to the engine, the left side regulator controlled gauge may say something like 70 psi after it drops, while the right side engine leakage gauge may say something like 65 psi.

You just plug a few numbers into your calculator, in the following manner:
You ask yourself, 65 psi leakage is what % of the 70 psi dynamic input pressure? And you punch into the calculator 65/.70 (don't forget that its point 70 here) and the answer comes up 92.8 (you could round up to 92.9 if you wanted), which means that the right side leakage gauge is showing or holding 92.8% as much as the left side input gauge. And because the original 70 psi dynamic input pressure was 100% of the dynamic input pressure, you simply punch into your calculator 100 “ 92.8 = 7.2% leakage in that cylinder, which is your final accurate answer for that cylinder. That's all there is to it.

For those who don't use much math, that may seem like too much trouble. But if you read through what was done a couple of times, and then actually do it a couple of times, you'll see that it's no big deal at all. And you'll be crunching the numbers freely after the first couple of cylinders.

There is no universally accepted input pressure for automotive leakdown testing. But the FAA (Federal Aviation Administration) has established 80 psi input pressure as their standard for leakdown testing on piston aircraft engines. And they allow up to 25% leakdown in those aircraft engines.

That 80 psi input pressure works perfectly fine for car engines too, so I use that as my input pressure as well.

And the reference chart I use for COLD leakdown testing on High Performance Engines is:

0-10 % = good condition

10-15% = though not ideal, still acceptable

over 15% = tear down and repair recommended for optimum performance

(for non-performance daily driver/grocery getter type vehicles, over 30% = tear down and repair recommended)

As a point of reference, my 540ci BBC Street/Strip engine shows a COLD leakdown of about 3%, using conventional Speed Pro rings, with a top ring end gap of .021 and a second ring end gap of .027

Here's the excellent leakdown tester that I use and like real well. It's from Goodson Tools and Supplies for Engine Builders.



http://www.youtube.com/watch?v=WgrfT0LFMhc



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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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Re: leak down test

Postby ljfen » June 30th, 2011, 9:43 am

Hey Grump, getting bad links for the inspection tool. A video inspection tool is on my list for tools. Just kinda expensive right now to justify the cost. The tool could be used in lots of places in the home too.
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Re: leak down test

Postby grumpyvette » June 30th, 2011, 10:17 am

fixed the link

BTW JOHNY468
POSTED THIS INFO

I just ran a complete compression and leak down test on my BBC today. It's a relatively mild 9.2:1 street motor I put together about 3 years ago. The cam is a Comp 288AR solid roller with 246/246 @ .050. I thought I would post these numbers here as an example of some real world test data and see if anyone has any input. The figures are cylinder, cranking compression and percentage of leakdown:

1 170 2%
2 173 2%
3 170 2%
4 167 3%
5 167 3%
6 163 5%
7 165 3%
8 171 2%

Number 6 is the only cylinder that looks a little weak. Other than that I think it's held up pretty well.

Johnny
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: leak down test

Postby grumpyvette » February 28th, 2013, 8:14 pm

if you do a simple compression test and find out a single or pair of cylinders read far less than most of the others theres an excellent chance your dealing with a defective head gasket, detonation damage on the pistons and rings, a broken valve spring that won,t keep the valve seated, or a busted valve or piston and be aware if it over heated a top compression ring that ring might have expanded enough for the piston ring ends to butt, expand and lock the ring in the bore for an instant, resulting in cracking or deforming the piston groove, if it did the compression ring seal will have been mostly destroyed(PERMANENTLY)
might also check the cam/lifters/pushrods. if valve(s) are stuck open, cracked cylinder head,no compression.
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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

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


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