Hi
Yes this is a known but rare problem. If you pop the bonnet, you may find that this valve has burst open:
This is the N7Q from the 2L safrane - one cylinder less but the basic block is identical:
It's on the back of that bellowed unit. I had this on my last safrane. The pipe at the bottom of the PCV / oil seperator under the inlet manifold, blocks up and then the engine can't breathe properly. Consequently it blows out the recirculation valve and oil vapour starts being pumped out which is then sucked along the top of the bonnet and sucked into the heating system.
If it helps, my oil seperator / PCV didn't need replacing like many volvos, it simply needed the hole in the engine to be unblocked (wire coat hanger did that nicely). If your valve has popped, the plastic that holds it in will be severely weakened so cable ties around the bit that it plugs into will hold it in place.
I ran mine like that for months and the engine coped for over a year like it however it soon got weaker and weaker - to the point where engaging drive would stall it. Once I'd done the job it seemed to have no ill lasting effects, engine was back to normal with more power than it previously had.
