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Old 02-29-2012, 07:16 AM
Quick99Si Quick99Si is offline
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Location: Chicago
 
Join Date: Jul 2011
Posts: 364
Mein Auto: 2004 M3 6MT
Retest cylinder with bad compression. Do it on a hot engine with the throttle plate kept open, and hope that it goes up due to testing error.

75psi of compression is well below any car engine's serviceable spec. If it doesn't jump up significantly, *and* there exists little variance across all cylinders, your next step is to do a leak down test to determine where the damage is. If it's the rings, you're looking at a complete rebuild; if it's a bad valve, you may get away with doing work on that head only. Those are not the only possible causes obviously.

Putting oil on the piston to fix this is a band aid that will last you a couple of miles, sadly.
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