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