My 94 850 non-turbo, 145k miles, seems to have high crankcase pressure. It forces oil and vapor out from underneath the oil fill cap. The leakage accummulates on the cylinder head underneath the spark plug wire cover, then runs down the rear of the engine. I was looking for some advice before going too deep in the repair process.

* the engine starts perfectly
* the engine performs perfectly
* the spark plugs look normal, no signs of oil deposits/contamination
* no exhaust smoke or oily residue in the tailpipe
* always performed oil/filter changes at 3k mile intervals
* I have replaced the flame trap recently

Is it possible I have something wrong with the oil separator that would be a root cause. Do the components associated with the separator ever get plugged. I haven't seen any service literature that specifies a routine maintenance on it. I thought it wise to asked for advice before purchasing a gasket set for the intake manifold removal.

The pcv valve needs to be cleaned, it is clogged.

In line with the other reply I still had high pressure after cleaning or replacing the flame trap and found I needed to clean out the ends of the vacuum lines as well (after about 110K miles). You can tell if any of the lines or the oil separator are clogged by blowing gently through each and finding where the air comes out or if there is resistance. For instance if the oil filler cap is on tight and you pull off the larger vacuum hose to the flame trap holder you should be able to pass air through the oil separator and out the dipstick hole; otherwise suspect the oil separator is clogged. If the dipstick is in tight you should feel resistance to air flow but should be able pass air out through the oil filler cap once you loosen it. Don't overlook the small hose from the flame trap holder to the vacuum tower on the manifold. That should have full manifold vacuum. In my case it was completely obstructed and needed to be replaced.

I have recently experienced the same symptoms relating to high crankcase pressure on my '93 854. Just yesterday I pulled apart the flame trap and related equipment to investigate and clean. I ended up removing the whole plastic elbow, flame trap and small hose to vacuum tower for a thorough cleaning outside the car. The flame trap was completely blocked with oily goo and sludge, as well as the rubber elbow and breather tube. a pipe cleaner rig, some paper towels and Q-tips did the job. I also recently replaced the gasket on the oil filler cap. Hopefully these fixes will do the job...
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'93 854 GLT, 154k

1) The vacuum lines to the flame trap could be clogged.

2) The gasket on the fill cap can be old and hard. Have you replaced it?