My daughter has a 2004 xc90 2.5t With approx 175k miles on it. Earlier in its life it appeared to have been well serviced but not so much in recent years. one of the problems I've found is the crankcase has positive pressure on it and will inflate a latex glove rather quicker when put over the dipstick hole. the car is loosing a fair amount of oil but there are no drips in the driveway or smoke coming from the tailpipe. Could the faulty pcv system be causing the oil loss? ive studied other members post about the pvc system and plan to remove the intake to address it and clean the throttle body at some point. All the hoses, that I can reach, feel intact and sturdy and I'm hoping I can just clean all the hoses out and empty that black catch can thing hidden under the intake or does it need to be replaced? The parts are like $350 for everything from Volvo so wanted to reuse as much as I could. Anyhow, if it won't help with the oil loss I'm not even sure if it's even worth the trouble..looking for some input here to figure out why it's loosing the oil

 

usually the problem with clogged PCV systems is that the excess pressure pushes out seals. I just did the PCV on my daughter's 850T after noticing leakage on both the front and rear cam seals. The problem with replacing the PCV is that you need to lift up the intake manifold to access the oil trap - and quite often the tubing and ports get clogged so the hoses should be replaced and the ports cleaned.

As to how/where you are losing oil - you should do a visual inspection first - anything dripping or oil covered? Pull the timing cover to check for leaks from the front cam seals and front main. Any dripping or stains from the bell housing could be the rear cam seals or the rear main. Check the oil cooler and lines. Finally, how does the firewall side of the engine look? the turbo oil return line gasket leaking can make quite a mess. If none of those are present, then you are burning the oil - could be turbo seals, rings, valve stems. Last thing to check is oil for foaming and sludge in the coolant in case you have a head/head gasket issue. A dry/wet compression test may clue you on the rings.

Last thought - what do you consider excessive consumption? if you are going 1 Qt/1000 then that's not too bad for a 175K engine, and you are probably looking at rings/valve seals. You may want to consider going up to a slightly thicker oil in the warm seasons (ie 10/40 vs 5/30) and try a high mileage oil with seal softeners.

 

Negative pressure is one sign of a clogged pcv system. Another is a strange noise coming out of your engine. I had the noise and replaced a bunch of things, serpentine belt, pulley, etc. Then I did the kit and it resolved the noise. There are kits with all the parts, seals, etc. Check fcp or ipdusa for the kits. YouTube has great videos to walk you through the repairs. Its not hard, but takes time to dig into the engine and get it done. I did mine at 150k miles. I just passed 200k, no noise since the new kit.

Good luck

 

In my experience - absolutely. I had positive crankcase pressure, with above-average oil loss. Oil consumption was significantly reduced when the PCV system was fixed.

See my post on a different thread (https://volvoforums.com/forum/volvo-...ghtmare-91338/), but I ended up replacing only two hoses, one was about $25 (from the valve cover to the oil trap, it's the piece that weaves from the top through the intake and into the catch can - it was completely split). The main culprit was a tiny plastic hose that is part of the very expensive 'breather assembly' - all I replaced was the clogged piece of hose, with 1/4" fuel hose from autozone. This was about 80,000 miles ago, no issues. My oil trap was perfectly empty and clear. Obviously this is hard to figure out without taking the intake manifold out...

There are other negative consequences to a non-functioning PCV system, as others have pointed out. It is quite possible that it pushes out a seal, or you loose lots of oil rapidly... I would address it irrespective of whether the oil consumption is high or not.