Excessive Crankcase Pressure Unresolved After Complete PCV Component Replacement

I have a growing problem with excessive crankcase pressure in my 90
240. I checked the usual suspects: the flame trap and hoses. All
were clear. I assumed the "breather box" was clogged or severly
restricted. I replaced the box and everything above it with new
parts, just to be on the safe side. I removed and checked the nipple
on the manifold. It was completely clear. The care still fails the
jiggle test miserably.

Oil had been leaking out onto the valve cover from the filler cap. So
when I replaced the PCV parts, I also replaced the brittle filler cap
seal with a new one. Now I am concernced that, with a good filler cap
seal, the pressure will have to find another outlet---like the rear
main seal. And I don't want to blow that or any other seals as a
result. I blew the rear main seal once about four years ago, and it
wasn't pretty (clogged flame trap and hose leading to manifold
nipple).

I wondered if the problem could stem from insufficient vacuum. I
checked for cracked vacuum hoses. They all seem to be in good shape.
I don't have a gauge (yet), but I do feel vacuum in the various lines
if I place a finger or the palm of my hand over the end with the
engine idling and at higher rpm's. It's the same at the intake
manifold nipple.

The throttle body has some carbon buildup around the point where the
main hose connects. The hose itself has engine oil in it along its
length all the way down to the Air Mass Meter. Obviously oil is being
forced where it shouldn't be. I considered removing the throttle body
and completely cleaning it. Is there a chance that carbon/oil fouling
within the throttle body could be reducing the vacuum in any way? I
do, however, feel vacuum at the manifold nipple at idle...

The car idles somewhat roughly and is much noisier than it used to be
several years ago. I have never done a valve adjustment on the car.
I've had my 240 for seven years and have added approximately 40K miles
since then, bringing the total mileage to about 160K. Can poor valve
clearance cause excessive pressure?

Any ideas?

Thanks in advance.

Zeke

 

I had to resort to blowing into the hose with the oil filler cap off to get
a feel for the restriction. Initially the system in my 765T was essentially
plugged (explaining why the oil all over the engine!) and was like blowing
through a small straw. When it was all cleared out it was like the pressure
of my lips when I pursed them to blow out all the candles on a birthday
cake.

The advantage of doing it that way is that the entier system can be tested
and each piece can be tested individually and in groups. For me, all the
restriction was in the parts you've already replaced or checked thoroughly.
But the problem has to be somewhere.

The oil coating in the intake is normal, the result of the ventilation
system working in the past. With a little luck it will be coating the ducts
again.

Mike

 

Which hose did you blow into to check the entire system? All my PCV
hoses are individually clear. But I am curious to see if there is any
of the overall restriction you described.

Zeke

 

Which hose did you blow into to check the entire system? All my PCV
hoses are individually clear. But I am curious to see if there is any
of the overall restriction you described.

Zeke

 

It might be worth having a leakdown test done. Worn rings can cause
excessive blowby which will pressurize the crankcase.

 

I unfastened the hose from where it attaches to the intake duct, just past
the MAF sensor. In the turbo it is the same as the turbo inlet.

Mike