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740 Excessive crankcase pressure, all PCV parts check out okay...

sclay

Member
Joined
Aug 27, 2006
Location
Bellingham, WA
Hey gang, before I throw the towel in and just plumb up an evilBay el cheapo catch can, could one of you fine folks see if there is something I am overlooking?

92 745, Turbo

Oil separator is clear (removed it, flows freely)
All lines are clear (also removed them, including the elbow and small line to the intake manifold, all clear)
Heater on intake tube is clear and unblocked

I did the "oil cap test" and the little dude just dances on the valve cover if he isn't latched down. It's a plastic cap from what I imagine is a later model Volvo. Maybe I did this wrong, but either way, that doesn't seem right.

Compression test yields 170-150-170-170 from 1-4. I don't have the tools for a leak down test.

Any idea what's going on? It sounds like plenty of folks have "had it" with the factory system and defaulted to a catch can setup, but I really dislike thinking that everything is working correctly and the system is still not operating as intended.

If anyone has any other ideas, or can see something I missed, or just needs to tell me to do a leak down test I'd greatly appreciate it. But this seems like a great deal of pressure, and it sure seems like my seals aren't into it.

Thanks
 
So are you popping the seals out or what is the problem exactly?
Static compression test may show good readings while the rings are shot and cylinder walls have oil on them. Seen it before. You may have a lot of blow-by under boost and stock 3/4 inch nipple on the turbo intake just can't flow that out of the case.
 
Did you check the oil drainback pipe under the oil separator box? That is what is clogged on my 93 n/a wagon. There was no unclogging it for me so I did something else as shown in the pcv mod thread.
http://forums.turbobricks.com/showthread.php?t=338673

You could probably use the oil cap or add a fitting to vent the valve cover to a catch can then from there to the turbo intake hose.

I did not! Thanks for pointing that out. I'll have to give it a look. I think general practice is to check on the tube for clogs right before changing oil? To prevent any gunk from making it's way through the system?

As for the one lower cylinder, I feel as if that should be within an acceptable tolerance, but someone who knows these engines a bit better maybe should clarify that. I can't be sure. The engine runs well.

I did the glove test, as best I can describe it, it doesn't "inflate" so to speak, but more like "flutter", sort of if you filled a balloon and then let the air out of the fill neck in one go. It certainly isn't pulling the glove down with any constant authority, and isn't filling it either. Pretty erratic.

As for which problem I am trying to solve, when I purchased the car, it appeared to have several oil seepage/leak issues for quite some time, and someone had been in there to mess with the oil box. As I know they can be a little bit of a problem child, I want to try and wrap my head around it's function and do my best to make sure it is operating as it should before putting the car in regular family service. Currently, I'd say at least the cam seal and distributor seal are having issues holding oil back, other areas I am still waiting to see what seeps out.

Thanks for the advice so far everyone!
 
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