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Compression test Posted by Ari [Email] ![]() ![]() In Reply to: Re: Head gasket failing and blowback (longish), Jason Lewis, Tue, 15 Mar 2005 07:52:10 Members do not see ads below this line. - Help Keep This Site Online - Signup |
A compression test is very straightforward - you can do it yourself with about $15 worth of easily-obtained test equipment. Basically, you pull the fuel pump fuse so the engine won't start, and pull the spark plugs. You screw a compression tester into a spark plug hole and turn the engine over a few times. The tester is just a peak-reading pressure guage. Any mechanic that can't do a compression test in his sleep should hang up his wrenches. See http://64.78.42.182/sweethaven/MechTech/Automotive01/default.asp?unNum=2&lesNum=7&modNum=6
One of many sites describing compression testing.
You really shouldn't need a Saab expert. Heads are heads, compression is compression. This ain't rocket science. It's nice to have a mechanic that saw a Saab before, though. As to giving you the worst case, I understand that is his approach, but upon hearing that, my first impulse would be to ditch the car. Even if the repair turns out to be less expensive.
As to damage, it all depends. If you are leaking a little oil out of the block, no big deal. If you have connection between passages, or between a passage and a cylinder, damage can occur. Is the engine running hot? Are you seeing oil in the coolant, or vice versa? Is your coolant level dropping? Are you burning oil? All of those are signs of head gasket damage. Those would be things that will get worse with time, and could cause damage. But if the compression is good, you aren't burning lots of oil or any coolant, then I'd say it's not a big deal, and keep driving it.
What signs are you seeing of blowback? Unusual noise in the intake?
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