I just picked up a '04 Jetta, unfortunately after finding this site and the buyers checklist. The seller, actually a friend who is moving overseas, had the car checked out by a local recommended mechanic, supposedly familiar with TDI's. He said no issues other than the tensioner causing a belt-squeeking when putting the wheel in full deflection left or right. So after finding the buyers checklist here i was checking to see if i had that skid plate, and saw the soot shown in the below pictures. I also noticed a thin, almost water-like in consistency, in the cup that surrounds the oil fill cap. Should i be concerned about these? Towards the left side of the block there is a "U" shaped pattern of soot - from having a GMC 6.5 turbo diesel in the past i would assume thats a gasket (and it looks easy to replace). My experience with TDI's is so far very limited. Previous owner was 2nd owner, purchased from dealership (it was trade-in for newer TDI apparently) at 85k miles or so. I picked it up at 135k and timing belt was not replaced by the second owner (and probably not done prior to 85k miles, so not done yet). Edit: A cleaning of the engine is also on the to do list after i either find out its nothing to be concerned about (diesels are dirty....soot...yada yada) it is diagnosed.