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lucittm lucittm is offline
Manassas, VA
 
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Join Date: Apr 2007
Posts: 1,211
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I built my own leakdown tester, the instructions were on the web. I had margninal compression on two cylinders on the same side (passenger). I performed a leakdown test and it confirmed I had broken rings because I could hear air escaping inside the engine and not into the exhaust or the intake like bad valves would cause.

If you shoot some oil into the spark plug hole and crank the engine over enough, you will almost always get some pretty good compression. The key is that the numbers don't need to be high, just consistent. My turbo with 7.5:1 will not generate as much compression as the 11.5:1 RSR (just guessing at the numbers).

So when you get readings like this 1-120#, 2-125#, 3-120#, 4-110#, 5-120#, 6-90# you know you have a problem, so you break out the leakdown tester. Do you test all six cylinders, no! Why test something that is good. I tested cylinder 4 and it only went to 70psi, then I tested cylinder 6 and it would not hold more than 10psi (from a 100psi source). When I heard the air flowing in the engine, I knew it was bad rings. I slapped in some new rings and the compression test results were even numbers across the board.

Mark
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1991 964 Polar Silver Metallic Turbo Coupe
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