I just picked a 94 850 Turbo this weekend. Got it cheap because we believed the head gasket was bad. After further inspection we (my dad and I) do not think it is the case. It was smoking white, but smelled oily. We pulled the hose out from under the valve cover that runs to the PCV and it quit smoking immediately. There is also a broken vacuum line that appears to go from by the turbo to under the exhaust manifold. So my real question is does this sound like a PCV issue, and does it sound like this vacuum line could be the actual culprit. Thanks

 

Couple of other checks would be oil on top of the cam cover (where the spark plugs are) and when the engine is running do you also see smoke coming out the dipstick tube?

In my case I had very little oil deposits on top of my motor, no smoke from the dipstick and when I went to service my system, I found gunk, and a plugged vacuum port on the PTC...and a slightly broken vacuum line and others lines quite chaffed.

Bottom line get a kit from FCP Groton or IPD (I like IPD's because of the murry style clamps compared to the OEM style clamp). FCP Groton has a great video on this repair too.

 

I can't think of why pulling the hose from the top of the "valve cover" would make a difference but the fact that it does would indicate you have a problem in there someplace.

Before I saw a black box cut open I always figured it was the box that plugged up from some complicated oil separation baffling. The box itself is dirt simple but the bottom can get plugged and you might be able to clean it out and just replace the rubber hoses. I did order the whole kit from IPD when I first got mine before I had done any research on it.

I'm wondering if your engine oil drain passages the black box plugs into and drains into are restricted with crud and pulling the hose let the engine suck standing oil/sludge into the intake and clear out the hoses running to the PTC valve on the plastic intake elbow that runs from the turbo to air filter housing.
If oil and crap from blow by and condensation can't drain and are building up in the box or hoses and getting drawn into the PTC it might be a reason for some smoking.

 

If you haven't done it yet I'd still do a test for hydrocarbons in the cooling system (head gasket failure). You can get the tool from most auto parts stores as a loaner and you only need to buy the fluid, under $10. It's just one more thing you can rule out or know it is bad and go from there.

You can youtube it and see how it works.

 

I doubt you have a bad head gasket unless it is bad at an oil passage but it would have to cross a coolant passage before getting into the combustion area.

Here is the block:



Here is coolant vs oil passages:

 

thanks guys. I will try to get a hydrocarbon test ASAP. My Chilton's manual is coming tomorrow, so my dad and I will be tackling the PCV issue first. I think he is still in awe of how complicated it is, compared to most GM style systems. RSPI, thank you for the pictures, visuals for me help a lot
and autorxray, there is oil under the valve cover which was the first red flag for me

 

I doubt that the manual will be a better tutorial than some of the DIY threads on these Volvo sites.

 

Do you think it will help explain the routing of the system well?