Compression test on car w/ coolant leak (Page 1/1)
FieroGT42 OCT 07, 07:51 PM
I can't find the coolant leak on my sister's Cavalier (2200 SFI, loses maybe 1/2 quart every 100 miles) so I did a compression check.

150, 90, 170, 160.
I tried putting oil in cyl #2 and it came up to 180 and held steady.
Testing repeatedly, it now comes up to about 180 and then leaks down to ~100 in only a few seconds.

Is this the rings? Could a head or head gasket problem do the same thing? The coolant looks murky, but no oil in the coolant or vice versa that I can see. Thanks.
GreenPlatypus OCT 15, 05:00 PM
Look for any coolant staining around the block and head. Drive the car to get it good and hot, then do a cooling system pressure test. Should be able to find the leak, look especially around things like the core plugs, and where the head meets the block, also all the hose connections. And also inside the car - maybe a bad heater core. Also check the transmission fluid - might be mixing from a bad cooler.

As far as the low compression, do a cylinder leak down test. Will tell you if you have worn rings (air through the oil fill), blown head gasket (bubbles in the cooling system/external air leak) or valves not seating properly (air through the exhaust/intake) <- not always that simple, but sometimes it is. Take it one step at a time and it'll be easy
FieroGT42 OCT 16, 03:50 PM
Did all that, found nothing. Couldn't find a certain intermittent coolant leak until I pulled the t-stat. I think the leak wasn't getting enough pressure past the t-stat even with the car warmed up, until it was actually being driven at highway speeds. I hope that's all it was. Thanks. +1 to your rating.

[This message has been edited by FieroGT42 (edited 10-16-2012).]