Various Compression Readings
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Joined: Feb 2005
Posts: 19
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From: east bay
Various Compression Readings
Thanks for all your previous responses to my posts regarding head questions. I have a 2000 Ford Excursion V10. I had a compression test done on the motor and the mechanic is telling me that he is getting uneven compression readings of 75, 140, 150 etc. The engine has 170,000 miles. What could be causing this? I want to make sure that I am not being taken for a ride. My engine eats about 1 - 2 quarts every 1000 miles depending on how much towing I'm doing.
Any wisdom would be appreciated.
Any wisdom would be appreciated.
FTE Leadership Emeritus
Joined: Jul 2002
Posts: 42,561
Likes: 423
From: Long Island USA
And, did he do a wet-and-dry check? Squirt some oil in the cylinder, if the compression comes up to within range of the rest of them, the rings are to blame. If not, the valves or a head gasket. And if there's not enough compression because of a head gasket, pressurize the cylinder with air and see if the coolant level rises (or bubbles) or if you hear it in the crankcase.
It's pretty easy to tell, IF YOU KNOW WHAT YOU ARE DOING, what's really wrong during a compression check.
It's pretty easy to tell, IF YOU KNOW WHAT YOU ARE DOING, what's really wrong during a compression check.
Tuned
Joined: May 2010
Posts: 434
Likes: 23
From: Somewhere in Alaska
One more thing. It doesn't happen very often, but if there is some debris in a spark plug hole the tester might not get a good seal. It doesn't take much of a leak to make it look like you've got low compression. And, if the debris stays in the hole, it can certainly be repeatable. Might want to make sure the holes are clean and do a confirmation test.
