Quote:
Originally Posted by Oracle12345
cant do a compression test with an engine cold....
So get the motor running then do the test at operating temperature
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Of course you can do a cold test. How relevant the numbers will be is questionable, probably within 10% of hot, but at least you'll have a base line to compare from cylinder to cylinder. If there are big differences you know you've got a problem. If they're close to each other then you'll have to determine if the numbers are acceptable. Maybe someone that has done a hot & cold test could chime in with the difference. If you've got hydraulic lifters, make sure you crank enough to pump them up before comp test or valves may not be opening enough to give you accurate numbers.
I bought a 300TD (617) with 338K miles and a rod knock. Didn't want to damage the crank/rods by warming it up so I did it cold. 370, 350, 320, 340.320. I deemed that acceptable considering milage to try to save the bottom end, rather than tear it completely down, so cold tests do have some merit. Hot test will always yield higher compression if everything is adjusted right and functioning properly.