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lucittm lucittm is offline
Manassas, VA
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Join Date: Apr 2007
Posts: 1,211
Define "functioning brain"...

The fact that you have a leakdown tester is comical after reading your post. Your post speaks to qualitative results "a compression leak..." Some of us with a functioning brain may want quantitative results, for example HOW MUCH is leaking past the rings or the valves. Your compression test will not tell you that.

Why? because if you have a compression leak and leakdown shows it is 10% then you can continue to drive the car with the knowledge that something is worn and not failed. Some people will tap the valves with a small hammer after a 10% leakdown shows which valve is leaking because you can hear the air flow upward (intake) or downward (exhaust) and the leakdown drops to 6-8%. That is some good quantitative results, right there.

My car was running fine, just using quite a lot of oil. The excess oil in the cylinder (see the picture below) kept the compression up. The leakdown indicated 90% of my supply air was going past the broken rings. The big difference is that the compression test is a dynamic test (the engine is turning over) but the leakdown is a static test (the engine is at TDC to with the valves closed or at some point along the piston travel to check cylinder wall integrity).

1991 964 Polar Silver Metallic Turbo Coupe
Old 08-13-2010, 07:33 PM
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