Just drove the 2001 S40 home, ran great--strong, smooth, quiet. Nice ride. It has 115k on the clock so its due for a timing belt, right? I got home and pulled the cover off to see how bad it was. Looks good...no hairlines anywhere, especially over the pulleys. Maybe someone replaced it but I doubt my luck is that good. No sticker on the cover either...but on the inside of the cover is something that alarmed me...a black, oily residue (opposite the exhaust cam).

The previous owner was clueless about cars and dumped a bunch of crap in the fuel tank in an effort to clear the CEL. There's also a similar residue on the lip of the tail pipe.

I had planned to replace the timing belt, tensioner, etc. Any opinions on what's causing the black residue?

thanks

 

Maybe the cam seal is starting to leak.

 

that seems to be the case, but is that because of a bad pcv system, or not? I'm an engineer so I like to find the root cause of the problem. If the pcv system is OK but the cam seal is not, then I can just focus on the cam seal.

My suspicion is that because of poor maintenance with previous owners, that the pcv system has problems. If that's the case, then what can I do to address that issue as well?

thanks for your help!

 

Yes if there is a problem in the PCV system it will cause the leak.
I would replace the vent box and check all lines. Then see if the leak slows down or stops.