2005 T6 XC90 Mystery Oil leak from Top Rear of Engine

[walczyk]

Hi all,

My parents recently bought a cheap XC90 ($2600) but didn't notice a big oil leak, it leaks down onto the exhaust and makes a big mess. I was trying to locate it, and after taking off the intake and intercooler hoses I think I've narrowed it down to either the valve cover, or turbo oil line. Are either of these likely to be the culprit? Should I look into replacing the PCV as well? I tried finding the wettest spot. Will the engine run with the hoses off? I think not, but I haven't had positive confirmation of the leak. Here is a picture I took This is after I cleaned it up some, the left pipe was even worse before, it was black with old oil.

I didn't see a valve cover gasket listed anywhere, and the oil line seemed to be $400 from Volvo. Would anyone be able to point me in the right direction? Thanks

[SuperHerman]

Pull the plastic cover spark plug cover and see what you have. I am seeing oil signs here which could be from a bad oil filler cap gasket and/or from filling the oil too quickly causing an overflow. From there the oil goes all over the place. You need to clean this up really well so you have a solid starting point. Take out all of the coils and check your spark plug wells for pooling and clean these up well.

Volvos do not use valve cover gaskets - the top cam cover is machined aluminum which runs a anaerobic sealant between it and the cylinder head to form the seal. There are 4-6 rubber o-rings (depending on number of cylinders (6 in your case)) that are also part of the seal. A serious clean up is required before concluding these are leaking.

Other leaks from the top could be the VVT solenoids and maybe a cam seal or four. Again you need to clean everything up.

Turbo leaks usually go down - not up. Stick your hand down there and feel the oil line off Bank 2 turbo (driver side) that goes into the block. It is below the aluminum runners so not likely the source, but I suppose air flow can be blowing it upwards. Bank 1 turbo is lower, but a similar set up. Usually the o-ring that enters the block leaks or the gasket from the oil line to the turbo. There isn't anything else that could leak on the oil return side. The oil to turbo side, in, should easy to determine - it should have a banjo bolt on top of the turbo, for bank 2. There are two crush washers, but unless they are played with shouldn't be leaking. Again clean them all up.

Over time your inter-cooler may have collected a good amount of blow by oil. You can disconnect the piping and try to drain it out and then monitor.

How many miles on the vehicle? Your turbos could be near end of life causing oil to pass into the aluminum runners. Your PCV system may not be working properly - check it (search glove test). You may have a slight air leak in your plastic plumbing, but this usually throws a code. Right now too early to tell what the issue is. You need to clean everything up well and then watch it daily until you find the source.