Skip to main content

My 1989 351 Windsor has developed a problem with oil coming up through the PCV valve and breather. It is to the point that oil pools in the air cleaner and drips out onto my headers when the engine is under any load. I believe this may be caused by excessive blow-by, but when I put my hand over the valve cover opening with the engine running, there is not much air movement. However, I suspect it could get much worse with the engine hot and at higher rpm.

That I would have enough blow-by to force oil up through the PCV valve and breather and not burn blue through the exhaust doesn't make sense to me, but what else could it be?

A friend suggested trying a different weight of oil to see if that could fix the problem.

Any advice on this would be appreciated.
Original Post

Replies sorted oldest to newest


you say oil is entering the air filter via the breather AND the pcv valve.

The pcv valve should have a hose connecting it to the intake manifold, below the carburetor. there shouldn't be a connection between the air filter and the pcv valve.

the pcv system removes a constant, small amount of gases from the internal engine, using intake manifold vacuum to draw the gases out of the crankcase, and processes the gases through the internal combustion process. the gases removed by the pcv system are replenished with fresh filtered air drawn through the breather.

Reading your post, I am under the impression that your pcv valve is connected improperly.


Of course you are right. I should have been more clear in what I wrote. Oil is coming into the air cleaner from the inlet breather. It also appears to be coming up out of the (correctly installed) PCV valve or hose judging by the pool of oil in the intake manifold pocket next to the valve and below the hose.

I have read elsewhere that one of the classic symptoms of a defective PCV valve is an oil-soaked air cleaner. I did the old shake test and the ball rattled around nicely, but I have also read that the shaking test is not definitive, and so my next step is to replace the valve and hope like hell that fixes the problem.
I had a somewhat the same issue several years ago with oil from the PVC valve into the air cleaner; what had happened (in my case) is that the oil return hole @ the rear of the head had gotten plugged up and was allow too much oil to stay in the head and was being drawn into the PVC valve. I would check your return holes as well, just "Knowing" is insurance.
Link copied to your clipboard.