Blow by Question
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Freshman User
Joined: Jan 2004
Posts: 35
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From: Boone Iowa
Blow by Question
I bought a 79 F150 300 Yesterday the guy said it had a little blow by> drove it 150 miles home checked the oil when i got home and it was 2 1/2 qts low so i e-mailed the guy and told him it used that much oil and he was shocked? He said the guy he got it from had a piece of rubber hose over the dipstick tube with a bolt in it and the dip stick was on the fender well and before i got there he put the dipstick in it. Is there any reason why oil would come out of dipstick tube?
Hotshot
Joined: Apr 2009
Posts: 14,333
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From: Stanley, VA
Sounds like excess crankcase pressure (blow by). With the excess oil consumption, a likely possibility is worn (very worn) or damaged (broken) rings.
Does it smoke out the exhaust? With a quart almost every 50 miles it should be either smoking incredibly bad or leaking like a sieve.
Another possibility is the crankcase vent system is plugged up. You can check the PCV valve but as cheap as they are it's easier and more reliable to just replace it.
Does it smoke out the exhaust? With a quart almost every 50 miles it should be either smoking incredibly bad or leaking like a sieve.
Another possibility is the crankcase vent system is plugged up. You can check the PCV valve but as cheap as they are it's easier and more reliable to just replace it.
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Freshman User
Joined: Jan 2004
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From: Boone Iowa
There is no smoke but where the breather cap on the valve cover is they ran a long chunk of hose run down along the engine why they would do this is beyond me. So the breather is not plugged either the engine was over hauled recently. I guess they tried other breather caps also. How do I check pcv valve? or just change it
Hotshot
Joined: Apr 2009
Posts: 14,333
Likes: 247
From: Stanley, VA
There is no smoke but where the breather cap on the valve cover is they ran a long chunk of hose run down along the engine why they would do this is beyond me. So the breather is not plugged either the engine was over hauled recently. I guess they tried other breather caps also. How do I check pcv valve? or just change it
My guess (and that's all it can be) is that the rebuild was done incorrectly. Either the rings are installed wrong, didn't seat properly or were damaged on installation or initial start-up.
I would suggest running a compression test and see what happens.
Senior User
Joined: Feb 2010
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On my '78 300, I had a little bit of blowby when I first got it. Nothing to the extent of yours, from the sounds of it, though.
Rebuilding the carburetor actually fixed mine. Or maybe it was that I got the vacuum hoses hooked up properly? Either way, check that.
I'd just replace the PCV valve. They're under 10 bucks anyway.
Rebuilding the carburetor actually fixed mine. Or maybe it was that I got the vacuum hoses hooked up properly? Either way, check that.
I'd just replace the PCV valve. They're under 10 bucks anyway.
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Elder User
Joined: Jul 2008
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My 302 V8 does the same thing, I have a rubber hose coming off the dipstick tube and going into a oil container and the reason being is oil was being shoved out the dipstick tube and spraying all over. But it don't use the amount of oil that you're going through..
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Posting Guru
Joined: Feb 2007
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From: Wingo, Ky
Sounds like somebody may have put news rings in a wore out egg shaped/oversized cylinder and called it good and it didn't work out for them.
My diesel tech teacher always said "You know why engines don't last as long after they have been rebuilt? People don't read the manual and check all the specs like they are supposed to".
I know you didnt rebuild the engine yourself but just a little advice for future use. Don't cheap out on a engine rebuild b/c it will end up costing you more b/c you will have to rebuild it again shortly down the road.
My diesel tech teacher always said "You know why engines don't last as long after they have been rebuilt? People don't read the manual and check all the specs like they are supposed to".
I know you didnt rebuild the engine yourself but just a little advice for future use. Don't cheap out on a engine rebuild b/c it will end up costing you more b/c you will have to rebuild it again shortly down the road.
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