Re: compress check?
Oh boy.<br /><br />JB just closed a good thread on this for the sake of some being confused....whoever they were.<br /><br />I do my compression tests warm. This way the viscous oil has circulated throughout the cylinder wall/rings providing a more realistic seal, and the engine's materials are expanded. Compression will generally rise with a warm engine. This should help diagnose any cracked pistons, cracked cylinder walls, broken rings, etc that have trouble building compression when heated. These type of failures don't always show enough % differential between cylinders when cold checked to make a proper diagnosis.<br /><br />Most manufacturer's compression numbers (that you compare to) will be measured warm, and most procedures to check compression will specify doing the check warm. <br /><br />There is also a "leak down" test that you can perform to isolate the problem further. This is done by pressurizing the cylinder or crankcase to find leaks.
