Volvo's PCV system...what's the deal?

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Feb 6, 2014
By PCV, I'm referring to the Positive Crankcase Ventilation system. Recently I was on a Volvo forum where someone was asking for a quote on getting the whole system refreshed (new hoses etc.). This got me thinking, why is Volvo's PCV system so finniky?! Even on the old red block RWD engines from the late 70's the system was overly complex and required more attention than any other car I've owned before, or since. Is there some benefit to it that I'm not understanding? or is it just another way to ensure Volvo owners will keep visiting their local Volvo service departments? Just my random Sunday morning thoughts coffee
I have never heard much about PCV issues with Volvo in the UK. Even when petrol versions were widely used by the Police and did huge mileages as motorway patrol vehicles I never heard about it from owners of these mega miles cars. Though the petrols are now rather rare as in the last 15 years or so diesel Volvos are more common than the petrols. I wonder why they are so problematic in the US?
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I hope you see oragex's recent "advice post" of his PCV work on either Matthew's or The "oil drip catch box" of the PCV system has 4 hoses on it. 1)short vacuum source, 2)drip return at the box's bottom, 3)the long one which goes to the base of the filler neck, 4)the other one in the middle. No big deal. The trouble is the box is mounted against the block and removal of the intake manifold is required to change out a $220 kit of plastic parts. That alone is the stupid design.
They do seem complex and time consuming to service, at least on my '98 model. Forced induction doesn't help, with how it has to vent to gases to the intake manifold when off boost, but vent to the turbo inlet when boost is up. More hoses and valves to get clogged or fail. That said the first one lasted until almost 150k miles before it plugged. Back then my dad owned it, and he had a shop do the repair. I'm now running synthetic oil, so I'm hoping to not have to replace it again anytime soon (knock on wood).
The sled has never had a port clog during my 20yrs of ownership. I only use synthetic oil. Two repeating problems I've had is that the plastic pipe running below the intake manifold cracks from heat/vibration. When this occurs, there is no longer any vacuum on the catch can and you now have an open, unmetered vacuum leak. This also causes hot oil vapor/blow-by to not be pulled out of the upper valve cover, causing extensive varnishing. In later models, these rigid plastic tubes were replaced with aluminum. Finally, weather plays a huge role in this.
We did hers about 12k ago. Nothing was clogged, but the flame trap and the line from the top of the engine to the flame trap was getting there much like an artery. Lots of yellow goo in the trap and carbon in the line. Thankfully, the flame trap to the block hole was clear and I didn't have to drop the pan. Oil consumption has gone down substantially after the replacement. Uses around half a quart during a ~6.5k OCI. The job was a pain, but I could do it much quicker a second time. Certainly wouldn't keep me from buying another. If the car saw A3/ B4 oil as well as highway miles her whole life, would it have been better? Probably.
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It's a good idea (everyone wants a catch can that drains to the sump) but poorly executed. It's hidden away under the inlet manifold, and everything is made out of plastic, which of course gets hard and brittle with age. My pipe under the manifold broke, and used the 5/8 heater hose trick because that's all I had available at the time last year. This year I revisited the system, looking good, no sludge...although there wasn't much last year anyway. I didn't like the idea of a rubber hose, but it's still ok, so eliminated some of the bends, using a right angle at the tank and turbo inlet, and steel pipe under the manifold. So now only short sections of heater hose. I'm going to forget about it now.
Originally Posted By: PeterPolyol
Wonder what kind of oil is used on those Police cars
They usually use the oil that is recommended by the manufacturer so I would suspect Castrol. That is what was the recommended oil in my 08 V50. 5w30 semi synth as a minimum meeting A5/B5 if I remember correctly. With an OCI of 12.5k if I remember correctly. If used in harsh conditions, taxi use, Police use, lots of idling etc then the recommendation was still the same OCI but 0w30 Full Synthetic only. That was for the 2.0d without a DPF. I can remember what the requirements for the petrols were unfortunately. Could using dino oil make a difference? Or would the warmer climate in the majority of the US make a difference? I have never cleaned or replaced a PCV system in any car that I have owned. I don't know anybody that has either. Maybe its down to US owners monitoring oil use more and trying to keep the vehicle optimised throughout the ownership period? I have noticed that US vehicles retain value better than UK ones often. A 10 yr old car is pretty much worthless in the UK when compared to what an identical car in mainland Europe or the US
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