Volvo AWD 850 Forum

Ready... turbos dont have a PCV. They do have a connection from the manifold to the intake which may need cleaning. It is between the engine and the firewall where the compressed air from the turbo comes up the large pipe. It is hard to see and easy to break, so be careful down there.
BTW, frequent oil changes and high speed running will keep it all clean.

Klaus
--
1975 164 w/173,500mi 1995 850T w/91,000mi, 1998 V70R w/128,000mi

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PCV maintenance 850 1997

posted by MadeInJapan on Thu Nov 30 15:19 CST 2006
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last visit: Sat Oct 2 06:34 CST 2010

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Klaus,
If I were someone not in the know, I think I would be confused with what you said. All FWD and AWD Volvo's have a "PCV System." This includes the oil trap under the intake manifold and the small hoses that connect from it to the bottom of the intake hose (right before it connects to the turbo) called the pcv nipple. www.fcpgroton.com has good diagrams of this...believe they call it the "breather system." Usually by 100K miles (and in many cases before), this needs "servicing" which typically means replacement of the oil trap as well as the hoses. The intake manifold has to come off to do this. I did mine almost a year ago....a turbo '98 S70.
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1998 S70 T5 Emarald Green Metallic (125K), 2004 V70 2.5T Ruby Red (45K), Previous Owner of Black '94 850 Turbo Wagon (Sold at 140K and miss her). My cars have been running so well lately they've got me worried.

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PCV maintenance 850 1997

posted by TomL on Thu Nov 30 17:06 CST 2006
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last visit: Sun Jul 25 18:24 CST 2010

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Davis,
Do you, or anyone else, know exactly what the PCV Nipple is supposed to do. I had mine out and it appears to be nothing more than a plastic device that connects the oil seperator breather hose and a vacuum line to the intake air sistem. What is the electrical connection for, an input to the ECM? Imput air temperature sensor? There is no valve in it and there is no direct connection from the vacuum line to the breather. I did clean the gunk out of the small vacuum nipple some time ago. I was going to replace it once thinking that it was defective but when I saw the new one (and the price) I determined that mine was OK.
My concern is that I cleaned the complete PCV system recently but I still do not get any vacuum draw at the oil filler cap, and I still get blow-by smell in the cabin when stopped and the engine is ideling. Maybe there is just too much blow-by for the system to handle. The car has 235K miles on it but does not burn any significant amount of oil. Less than 1 qt. between changes @4-5K miles.
The 850 PCV system seems over designed and unnecessarily complicated. Why couldn't a PCV valve like on my Dakota work just as well? Direct connection from the crank case to the intake vacuum. That is also a flame trap.
Does anyone have any answers?
--
Tom 69-1800S, 72-1800ES, 96-850T,2000-S70 GLT-SE

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PCV maintenance 850 1997

posted by MadeInJapan on Fri Dec 1 16:08 CST 2006
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last visit: Sat Oct 2 06:34 CST 2010

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Not sure I can answer all of your questions, but I'll try to answer a few. The pcv nipple apparently has a heating unit in it so that it turns any oil there into a vapor before it is fed into the intake to turbo hose. This is really only needed on start-up because the oil heats up as an exhaust and recirculates eventually anyway. One of the ideas of having a heating unit there is to also keep oil there from clogging (though it still eventually does). If you're still having positive pressure, it could be that the short hoses (there are 2 of them) that connects it up to the side of the block (where it butts up to) are clogged. Did you also swap the oil separator under the intake manifold out when you cleaned the system? Any clogging in the pcv lines render the whole system non-funtional. I agree that it's way over-engineered and possibly another system like you mentioned might work just as well, but I'm also afraid that putting a different system on your car might be sensed incorrectly by the ECU and set a code.
--
1998 S70 T5 Emarald Green Metallic (125K), 2004 V70 2.5T Ruby Red (45K), Previous Owner of Black '94 850 Turbo Wagon (Sold at 140K and miss her). My cars have been running so well lately they've got me worried.

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PCV maintenance 850 1997

posted by someone claiming to be Frank on Thu Nov 30 14:44 CST 2006 [RELATED]

Thanks Klaus! It's just what I needed and I hope this helps others who might be confused about PCVs and turbos.

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