390 oil problems
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Junior User
Joined: Nov 2005
Posts: 95
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From: Northern UT
390 oil problems
My 390 is blowing oil out the dip stick, I have replaced the head gaskets, intake manifold and still cant figure out whyI have heard that the rings may be bad but I dont understand how bad rings would preasureize the oil pan
Any thoughts or ideas would be helpfull
oil
Senior User
Joined: May 2004
Posts: 185
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From: Bedford Hts, Oh
O.k., if the ring/rings are bad, the pressure from the ignition in each or the cylinder can squeeze thru. Just like water, it wants to go through the path of least resistance, the oil pan. And when it builds in there, it wants to escape out the dipstick. Pull your plugs. One or more make look different, even have oil on it. At least your not blwing out plugs. But, there could be a problem with your oil pump, as well. What's your oil pressure read?
Elder User
Joined: Feb 2002
Posts: 987
Likes: 2
From: East Bend, Carolina, U.S
The oil pan is not the only thing that gets the pressure buildup from blow by. The inside of the block (crankcase), oilpan, and valve covers are all affected.
All engines have some blow by past the piston rings caused by the combustion in each cylinder. The blow by can pressurize the crankcase and blow out a dipstick if the PCV valve isn't working properly. Even a good PCV system cannot overcome a large amount of blow by when an engine has worn rings, cylinders and or pistons. Even a recently built engine can have excessive blowby if there is a damaged ring, piston and or cylinder.
If excessive blow by is present then at idle even with the PCV system working properly you can see the blow by escaping through the valve cover vent or even the dipstick tube. You may need to drive the truck around a bit and get it warmed up to really see it. It should look a bit smokey and you will be able to feel the pressure if you partially block off the valve cover vent.
So, if you notice this blow by at idle then just think how much is present under acceleration and loads!
Last but not least, a compression test on cylinders is needed to know what you are dealing with for sure.
All engines have some blow by past the piston rings caused by the combustion in each cylinder. The blow by can pressurize the crankcase and blow out a dipstick if the PCV valve isn't working properly. Even a good PCV system cannot overcome a large amount of blow by when an engine has worn rings, cylinders and or pistons. Even a recently built engine can have excessive blowby if there is a damaged ring, piston and or cylinder.
If excessive blow by is present then at idle even with the PCV system working properly you can see the blow by escaping through the valve cover vent or even the dipstick tube. You may need to drive the truck around a bit and get it warmed up to really see it. It should look a bit smokey and you will be able to feel the pressure if you partially block off the valve cover vent.
So, if you notice this blow by at idle then just think how much is present under acceleration and loads!
Last but not least, a compression test on cylinders is needed to know what you are dealing with for sure.
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