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

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1990 Volvo 240 Sedan Pittsburgh, Pennsylvania
Reply to
zeke.woods
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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

Reply to
Michael Pardee

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

Reply to
zeke.woods

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

Reply to
zeke.woods

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

Reply to
James Sweet

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

Reply to
Michael Pardee

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