What is this pipe?

[motco]

Just to the left (as viewed from here) of the oil filler and hard against it? My daughter's 850 estate (B5204S engine) has this pipe and it's got a hard plastic small diameter additional pipe running parallel to it but unconnected at one end. The engine is showing symptoms of crankcase pressure - oil blowing from the dipstick hole - and I suspect a blockage in the crankcase ventilation system. Is this involved?

[Rockatansky]

Yes, thats part of the PCV (Positive Crankcase Ventilation) system.

These are well known for being neglected, failing, and causing excessive crankcase pressure and ultimately oil leaks.

It is a diy-able job and there is a comprehensive 'how-to' here:

http://www.volvoforums.org.uk/showthread.php?t=469...

[motco]

Rockatansky said:

Yes, thats part of the PCV (Positive Crankcase Ventilation) system.

These are well known for being neglected, failing, and causing excessive crankcase pressure and ultimately oil leaks.

It is a diy-able job and there is a comprehensive 'how-to' here:

http://www.volvoforums.org.uk/showthread.php?t=469...

Rockatansky, many thanks! This one, my daughter's, has the smaller pipe (manifold blow-off?) connected only at the cam casing end and not at the outside world end. I have to try to discover where it goes. The crankcase pressure is such that oil has been blowing from the dipstick tube and soaking the spark plugs. No, I don't know how it gets under the cover but the plug recesses are full of oil! It's a 100,000+ mileage car but runs well enough. It will have a bit more piston blow-by than a newer unit though.

[Rockatansky]

I'd get it sorted sooner rather than later if I were you, as the next thing to go might be the crankshaft main seal - and thats a bit more of a PITA to sort.

The small pipe from the rocker cover connects to a separator tank which is attached to the block (hidden by the inlet manifold). There are also pipes which link up to the inlet before the turbo.

The chances are that the separator tank is blocked and that the other pipes are also split.

When I got my V70 it had an alarming amount of oil under the plug cover and it also leaked into the distributor cap causing quite a pronounced misfire.

To reiterate: get it changed!! - and get a new 'o'-ring for the oil filler cap too, they go easily too.

[motco]

Thanks Rockatansky, I will. I simply have to get my daughter to stand still for five minutes and hand over the car! It's a normally aspirated engine, by the way (the photograph's not hers), but I don't think that alters the urgency. She's off in her 1984 Bedford CF campervan in a few days, that's my chance! Thanks again.

Edited by motco on Wednesday 5th August 09:08

[GreenV8S]

I think most cars these days have a PCV check valve, but older cars (such as my TVR) sometimes use a simpler (cheaper) system with two breathers: a small restricted breather downstream of the throttle that applies suction (via the restriction) under part throttle (hence the 'positive' part of PCV) and a much bigger unrestricted breather connected upstream of the throttle that allows the crank case to vent under full load. From your description, I suspect the setup here may be similar.

[motco]

Well today I got the car to start after fitting a set of new plugs and mopping up the oil from under the cover over the plug apertures. It took a lot of cranking to start it and it was totally gutless to drive so I reckon I need to sort this breathing set up. There's two small diameter pipes disconnected; the one that runs in parallel with the PCV larger pipe from the valve gear chest, and another the function of which I do not yet know but that emerges from under the injector rail. Also there's a split in part of the ducting between the air filter and the inlet manifold which could, I assume, upset vacuum sensors connected to the engine management unit. All in all it's a bit of a dog's breakfast and I shall be spending a couple of days getting it right.

A schematic of the non-turbo PCV system would be a great help if anyone has one, please.

Edited by motco on Wednesday 5th August 18:28