Oil Inside Intake Manifold Opening, Causes?

Flyingboy · Flyingboy's Garage

I see in Wayne's tech article on Intake Manifold removal, in the pictures, oil just inside the IM opening, where throttle body mates up to it. And inside bottom of throttle body. I noticed this on mine too.
What could be the culprit? Big problem? or more normal?

Thanks

Manolito · 01-25-2010, 05:40 AM

A little oil is unavoidable. If the engine is high miles or you drive hard (high RPM) you are going to get some oil mist in the vent tube from the front of the valve cover.

In an ideal world, the flow through that vent would be clean air coming from the intake toward the valve cover. At idle, the PVC valve closes, so that flow reverses. Also at high RPM or on a worn motor, that flow reverses.

If the PVC valve is full of gunk, it will not flow as much, so you will get more flow toward the intake from the vent pipe.

We recently pulled the PVC valve out of daughter's '97 with 230k miles on it. The drain hose had turned to mush and was nearly blocked with sludge. We cleaned the PVC with solvent, and then decided to go ahead and replace it while we had it off. BMW does not stock that hose, but a foot of hydraulic hose from the auto parts store fit perfectly.

coolbear1 · 01-26-2010, 01:11 PM

Manolito, I have been looking for something on my 93 that resembles a PCV valve with no success, there is however a plastic venturi type thing in the fitting that connects the hose you refer to in this post. It has no valve in it. Is this the PCV?
Also my 93 has been passing oil from the engine to the intake for as long as I can remember, it only becomes a problem whe n it gets enough gunk in it to stop moving through to combustion, it will plug up the idle control valve.

Manolito · 01-27-2010, 06:15 AM

I responded to this last night, and my response did not post for some reason.

The PVC is a black object about the size of your fist with a funnel-shaped cyclone oil droplet separator on the bottom and a large vertical diaphragm on the top. It plugs into the intake manifold from the engine side, beneath the manifold. To access it, you need to remove the two bolts that hold the power steering reservoir and pull it aside. There are two or three 10 mm bolts that hold the PVC in place.

I was not able to suck it shut to test it the way I can with a small conventional PVC valve. It apparently takes a significant amount of flow to suck it shut.

coolbear1 · 01-28-2010, 04:41 PM

I must not have one on my 93, the only thing I have in the area you discribe is the charcoal canister and purge valve, it connects to the bottom of the throttle body on one side and the gas tank on the other. It removes vapors from the gas tank, and sends the to the engine to be burned. There is nothing connected to my intake manifold other than the vacuum to the fuel pressure regulator, the vacuum to the valve cover, and the Idle air, and throttle body.