Does anybody out there know what would cause a good running 352FE to suddenly start having extremely high oil pressure and blowing it out through the valve cover breather and the dipstick tube?

 

are you sure the pressure is high and not a plugged beather.

 

yep, I replaced the breather twice and the pcv valve.

 

never seen this but I've heard that if breather get's pluged a oil pan could blow, if fuel vapor is built up inside? Has anyone seen this? Seemed to have to be a lot of fuel to do that.

 

bad rings and blowby?

 

I don't think it's the rings because it runs too good and doesn't smoke or burn any oil at all. I recently replaced the intake manifold gaskets and cleaned what little sludge was in there but I was having this oil pressure problem before.

 

Oil pressure wouldn't do that. Excessive crankcase pressure, most likely a bad ring or burned piston. Run it with the breather off and see how much air comes out.

 

I once had a 327 Chebby with a cracked piston skirt that did exactly the same thing, especially when I really got into the throttle.

I guess that would fall into the same category as Ford_Six's post -- excessive crankcase pressure.

 

How about a stuck relief valve on the oil pump, had one do that on a 428 in my Galaxie and it would peg the manual gage.

 

We may be chasing our tails here, so let's get some clarification.

How much oil pressure do you actually have?

Do you have a manual gauge, or is it the factory electric gauge?

Are you just assuming that high oil pressure is what is causing the engine to blow oil out the breather?

 

I think 70_RangerXLT has hit on a key issue, as "oil pressure" and "crankcase pressure" are 2 very different things and rarely have much to do with each other. Oil pressure refers to the pressurized oil between bearings and their associated shafts/parts to theoretically keep them from actually touching each other to reduce/minimize wear as well as lubricating them. This pressure is provided by the oil pump sucking oil from the oil pan, pressuring it and then pumping it through small passages to various moving parts. This pressure is then released by the oil leaking/squirting/flowing out of the tight clearances between the bearings and their associated parts and further "splash" lubricating such areas as cylinder walls, timing chain etc. This oil is then "collected" by valve covers, timing cover, etc. and then returned (by gravity) through a series of passages to the oil pan. The whole return system can be thought of as the "Crankcase" even though many think of only the oil pan as such. Crankcase pressure is usually caused by leakage of cylinder compression/combustion pressure either past the piston rings, bad valves and guides and/or cracks/leaks in heads/block/head gaskets.
My apologies to those experienced mechanics for my somewhat elementary explanation, but misinterpretation of terms and misunderstanding of how things work can lead novices into costly/unwarranted repairs.
Thanks
Gene

 

It has the original factory gauge. It has always stayed in the normal range but now it starts out high (like pegged) but after idling 15-20 minutes, it will slowly go down a little to slightly above normal as the temp goes up to normal. This started about the same time I started noticing oil coming out of the breather, the dipstick tube and the distributor base every time I drive it more than 5 or 10 miles. I've never had an engine do this. It sounds like it has high crankcase & oil pressure but it runs so perfectly I can't believe there could be a bad piston or ring(s).

 

Even though both conditions appeared at roughly the same time, I don't believe they're related. Neither should have anything to do with the other.

High oil pressure could (and probably is) be caused by a sticking relief valve in the oil pump. Another possibility is a clogged oil passage, but it would have to be severely clogged, and in one of the main passages.

Excessive crankcase pressure is caused by compression bypassing the piston rings and getting into the crankcase. Bad rings, burned piston, cracked piston are three things that come to mind. If the PCV Valve isn't functioning correctly, that could also contribute to the oil blowing out, but it's not a cause of high crankcase pressure. One other thing, if you've got a head gasket that's leaking somewhere besides between cylinders or at a water passage, compression could be coming through that into the crankcase. It wouldn't take much of a leak to build pressure in the crankcase.

My advice would be to run a compression test (warm engine), both dry and wet. I suspect you're going to find some inconsistencies there.

As for the high oil pressure, have you changed to a thicker oil, by any chance?

 

The ONLY thing that causes oil to be "pumped" out of the breather and dipstick holes, both, is blowby. You got some really bad rings or a holed piston. Sorry! With your engine running is there a "plume" of gray/blue smoke shooting out of the breather hole? If so, (and I'll bet my left one it is) then it's time for you to refresh your block internals. Mine does the exact same thing. That's why it's in my shop with the front end off waiting to have the engine yanked.

 

I don't think that oil pressure would blow oil out of the breather or dip stick tube. I'm with the others on this one, bad rings colapsing under the combustion pressure. I had a 351w do this to me years ago. I kept driving it and watching the oil level, one day after school it had enough and puked all the oil out very fast. That engine is now a very large boat anchor. Like somebody said before do a compression test. Do the first test when it is cold, then get it up to operating temp and check it again. You would be surprised at how well an engine will run with 2 or 3 cylinders very low on compression. Keep us posted on what the compression #'s are.