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Old 05-17-2007, 04:11 PM   #1
BoostedSwede
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Question oh yay!! another thread about high crankcase pressure!

Alright, first of all, I searched, I promise! I still couldn't find an answer to my question.
The vehicle in question is a 1994 940 turbo, with 163,000 miles. I had been having issues with my oil dipstick popping out of its tube, and oil weeping from the oil cap. So, I searched on TB and discovered that I probably had a clogged PCV system. Of course, I put in a new breather box and o-ring, a new PCV nipple, and cleaned out ALL of the hoses relating to the PCV system. They were all completely spotless when I was done. All seemed fine for about a week, and then today I got home after some spirited driving only to find that the dipstick had popped out yet again, and the oil cap was weeping. The seal on the cap and the o-ring on the dipstick are both about 5 months old. So what could be causing this?!! Thanks for any and all help!
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Old 05-17-2007, 06:15 PM   #2
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Maybe something got hooked up improperly, or you forgot a check valve somewhere...
if not,
excessive piston blowby?

compression test will tell the full story.
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Old 05-17-2007, 06:40 PM   #3
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Default piston blowby?

the car runs absolutely flawlessly other than this one issue. no smoke at anytime, uses no oil between changes except for what is blown out of the dipstick tube when it has it's little crankcase pressure tantrums! wouldn't excessive blowby be noticeable?
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Old 05-17-2007, 07:27 PM   #4
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i mean combustion gasses getting by the rings.

you said during spirited driving? usually means boost is being used. which increases the chances of that happening.
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Old 05-17-2007, 07:51 PM   #5
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oh. duh. can you tell i'm having a stupid day?

so assuming it is indeed blowby, what causes it, and how can I fix it? If it's not blowby, what are some other possibilities? I know that I have a small exhaust leak at the manifold, but I doubt that it has anything to do with it. Further information...the car is at stock boost with a K&N cone filter and new plugs, wires, cap & rotor, fresh oil and Mann filter, all new vacuum lines, and the headgasket was done about 6-7,000 miles ago.
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Old 05-17-2007, 09:30 PM   #6
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if it IS piston blowby, i believe the only way you can check is a compression test.


but double check everything vacuum line related...you'd be surprised that SOMETIMES something looks connected but could be coming loose or not sealing.
also, double check the nipple for the PCV line...
maybe spirited driving (which it might not have been accustomed to during most of the cars life) may have knocked something loose, and clogged it?

also, do the oil filler cap test...
turn it so its loose, but dont take it off. if it dances around, excess crankcase pressure. if it "sucks down" with some vacuum, and pulling it off changes the rpm a touch it should be ok (at least at idle).

and if it IS getting by the piston rings, i do believe a rebuild is the way to fix it...at LEAST replacing the rings, if not boring out and replacing other things.
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Old 05-17-2007, 09:39 PM   #7
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cool. I'll definitely double check all of my vacuum fittings, as I had lots of vacuum related problems when I first bought the car. I'm also going to clean out the vacuum fitting on the intake manifold for the breather box.
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Old 05-18-2007, 12:36 AM   #8
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I just pop the dip stick a little and tie a rag around it - every so often I change the rag or the oil will just drip down. Of course my car has a hard 260K miles on it so some some blow-by is expected (and piston knock/slap too).

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Old 05-18-2007, 12:48 AM   #9
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Just in case you didn't, try replacing the o-ring that lives on the dipstick itself. They go hard and shrink and barely look like o-rings after a while.

edit: oops you said they were pretty new. Sorry. Try replacing them anyway.
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