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How does one perform a leak down test? I've got a little oil burning going on and I'd like to determine if it's only valve stem seals, or if bottom-end work is needed. I get a puff of smoke on shifts, and when I punch it (the read hatch seal leaks the smoke into the rear of the cabin, so it's easy to tell).

Thanks,

Kurt
 
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Kurt,

I'm sure there is a specific test for that but I don't know it. I would start with a compression test. That should at least get you in the ballpark for the shape of the rings and cylinders. Good luck. John
 

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It's been a while but you put your [email protected] with both valves closed. Then, using your leak tester, blow compressed air into the cylinder through the spark plug hole. How much air comes out where tells you where the problem is. If it comes out throught the intake, it's an intake valve, through the exhaust = exhaust valve, etc. You can compare cylinders to determine if rings are worse on 1 cylinder than the others. The engine may turn if you aren't at TDC. Use leak down test in conjunction with compression check.
 

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John is right.

Do the wet and dry compression test. The dry test will give a baseline for each cylinder. Then squirt a little oil into the cylinder, and test again. If the readings go up (more than just a little) with the oil in the cyl, then the rings are suspect. If the readings stay roughly the same, you may have bad valve stem seals.

What you don't want to find is one cylinder lower in compression than the rest.

For specifics on the different tests possible with a compression gauge, read the directions on the package. It should explain how to perform a leakdown test (monitoring pressure drop over x-time).
 
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