Hi
Below I posted about a major service on my 2006 XC70 with 175K miles. We replaced a failed turbo with a good, low mileage unit. Also completely serviced and replaced the PCV system. Never touched the oil pan. The car drives/runs amazing. However, apparently I celebrated too soon. Immediately thereafter it developed an oil leak at the rear of the oil pan which we cannot resolve. We have removed and resealed the oil pan 6 times. Started with anaerobic sealer, moved to Volvo brand anaerobic. Even tried RTV and finally replaced with a new oil pan. Same leak every time...no better, no worse. Checked RMS and turbo oil return line to confirm it is not coming from there.
Running out of ideas. Any thoughts?
Thanks
Bob

 

Hi
I like to follow up posts with what I have learned so hopefully others can benefit. When we serviced the PCV we went 98% of the way there and it resulted in a pressurized crankcase which blew out the pan gasket. Fortunately, that's all that happened as I have learned that others blew their cam seals which is a much larger job. After a thorough smoke test, we finally tracked it down to a cracked tube in the Crankcase Breather Pipe Assembly. This is Volvo PN 30731068 and a $225 part. Thus, since it was so expensive we cleaned and reinstalled the original which was a mistake. There is a tiny hard plastic hose wrapped under all the insulation which gets brittle with age/heat. Apparently it cracked when we removed it to clean it but, didn't realize it because it wrapped under foam insulation.

This breather assembly has three hoses. The first runs from the PCV box and attaches to the bottom of the intake manifold (IM) via a banjo bolt. This is the hose which cracked. It provides vacuum to the crankcase during the "idle circuit" to vent blowby from the crankcase into the IM. In addition, the banjo bolt has a special one-way check valve that closes to prevent reverse flow. When the turbo spools up, the check valve in the banjo bolt keeps boost pressure in the IM from being routed back into the PCV box and crankcase. The second hose is designed to vent the crankcase blowby when the IM is under pressure from the turbo. This "boost circuit" hose runs from the PCV box to the fresh air intake side of the turbo (the hose b/t the air filter and the turbo fresh air intake). The last hose is a coolant hose which runs from the thermostat housing to the far side of the engine block. Its sole purpose is to flow coolant and warm the other two hoses and prevent them from clogging with oily engine vapors.

So, had to remove the intake manifold again, Replace the Crankcase Breather Pipe Assembly and replace the Banjo bolt with Volvo updated PN 31325709 (this has the special check valve in it). I used this as an opportunity to remove and clean the throttle body. Removed and resealed the oil pan. And...all is good.

Moral of the story is if servicing the PCV, don't cheap out and also replace the Crankcase Breather Pipe Assembly and use the updated Banjo Bolt

Bob

 

Thanks for the write up.