370 oil usage
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370 oil usage
Hey guys
I have an '84 370 from a f-700 truck that suddenly started using a lot of oil. It's fouling out the #7 plug. I did a compression check and it has good compression (120+). Could it be I broke an oil ring on that cylinder without losing much for compression? Or could it be such a thing as a valve seal disappearing? The truck has about 150000 on it. Should I close my eyes and pay for a complete overhaul or try to figure out why just one cylinder is using oil?? thanks
I have an '84 370 from a f-700 truck that suddenly started using a lot of oil. It's fouling out the #7 plug. I did a compression check and it has good compression (120+). Could it be I broke an oil ring on that cylinder without losing much for compression? Or could it be such a thing as a valve seal disappearing? The truck has about 150000 on it. Should I close my eyes and pay for a complete overhaul or try to figure out why just one cylinder is using oil?? thanks
Postmaster
Joined: Nov 2001
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From: Escondido, CA
Try doing a leak down check instead of the typical compression check. The leak down will tell you if the rings are bad. It may not show the valve leaking oil but it will rule out the broken ring possibly. You can also take off the valve cover and physically check the valve for a bad seal or worn guides with a little more removal. You may also have an intake gasket leak that is sucking oil in through the lifter valley. It's hard to say sometimes. To be honest though, with that many miles on it I would concider the rebuild.
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Joined: Jan 2006
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From: Fort Worth,Texas
Originally Posted by Schmittys diesel
I thought about an intake leak as well, but why would an intake leak foul out only one cylinder?
Good luck
Bill
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I would be extatic if it would be as simple as an intake gasket. But I'm still amazed at how much oil this thing is using. It was burning 2 quarts + in one day. Granted we were driving it hard at that time, but still...2 quarts??? I couldn't really imagine that much going through the gaskets unless they were completely non-existant. Another thing..If I would take the oil filler cap off and plug the PCV I would get the slightest air pulsation from the top of the valve covers. And now that I'm thinking of it...If I remember right, the air cleaner would be almost wet with an oil residue. Now that I am recalling all of this, it is beginning to sound more and more like intakes.?? What do you guys think????
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Postmaster
Joined: Nov 2001
Posts: 3,351
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From: Escondido, CA
The air pulsing out of the filler is normal. That is the result of the pistons moving up and down with a little air from the chambers leaking by the gaps in the rings. I wouldn't be too alarmed about that. The PVC pulls gases out of the crank case to reduce the formation of acids in the oil. The wet air filter could be from oil vapors being sucked in. What side valve cover is your PVC on?
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