paul,
The PCV valve for Turbos is in the intake air pipe near the turbo. Hard to get to. There are two rubber hoses going to it. The smaller one (with rubber elbow) is the vacuum line and the larger one is the hose to the crankcase. Remove the vacuum line and try to insert a small drill. You will probably encounter some resistance. Use the drill to clean it out. When this port is plugged the PCV system fails to work and allows pressure to build up and blow oil out the dip stick, fill cap, and rear seal.
Good luck,
--
Tom 69-1800S, 72-1800ES, 96-850T,2000-S70 GLT-SE

Volvo's pCV valve is the flame trap located just in front of the throttle body on the back side of the elbow in the hose from the air cleaner to TB. The flame trap element is a nickel sized piece of plastic with many holes that fits inside the holder. Turbo cars don't have a flame trap element and I think volvo stopped its use with all 1997 models. The problem with flame traps is they need to be cleaned fairly often. If they were neglected and get plugged up, crankcase pressure would rise and blow engine seals, very expensive on FWD cars as tranny had to be removed to getat the seal. There are two hoses that run to the frame trap holder. The larger one runs down to an oil vapor vent box (forget the technical name of it right off) bolted to the side of the block and very hard to see on an 850. Crankcase oil vapor vents thru this box and travels up the hose where it is injected into the air going into the engine to be burned. If that oil vent is plugged at the block, it will run your crankcase pressure up as well but I'd think this was very unlikely if you oil is changed on time. Look in the FAQ section of the 2-700 forum under high crankcase pressure.

jB

jB