Compression test question.
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Joined: Jan 2010
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From: Cuyahoga Falls Oh
Compression test question.
Today I decided to change the plugs on my 92 F150 4.9L , since I was pulling everything a part I decided to do a compression test. Cylinders 1,4,5,6 all tested at 160 PSI while 2-3 tested at 130 PSI. The difference has me a bit concerned that I might be losing a head gasket. There is no oil in the coolant, and the oil is clean, and doesn't sizzle when droped on a hot exhaust manifold. For the most part, other then a occasional stumble, the truck is runing okay. All 6 plugs look fairly good, and show no signs of oil, and there's no smell of antifreeze under the hood. Vacuum gauge shows 20 inches with no flutter. The truck does appear to have a small amount of blow-by as there is a small oil stain on the air filter near the PCV filter.
The truck turned 190000 miles today.
Should I be worried about a possible head gasket? or did 2-3 just wear a little more then the other 4?
The truck turned 190000 miles today.
Should I be worried about a possible head gasket? or did 2-3 just wear a little more then the other 4?
Last edited by ReFlectiveMan; Jan 23, 2010 at 04:16 AM. Reason: added blow-by remark
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190k I wouldn't sweat it. You're real close to the 20% difference that I hear is the cut off for normal wear and tear differences.
You could try and see if the compression loss is in the head or rings via the oil in cylinder method. If its the head, put it on the to do when convenient list.
You could try and see if the compression loss is in the head or rings via the oil in cylinder method. If its the head, put it on the to do when convenient list.
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Joined: May 2008
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From: In my own world
squirt a small amount of oil in those cyls. if the compression raises, it's rings. if not it's valves. put 60 lbs of air to the cyls, and listen on intake side, or exhaust side where leaking. more than likely, you have carbon buildup, and just need to run some sea foam through it to clean it.190,000 miles is not a lot on a well mantained 300.
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