A bit quiet this week as I've been waiting for parts and working on another engine. Mike came over on Thursday and gave me a hand with the cam chain tensioners, and I completely forgot to take any pictures, but thats well documented elsewhere anyway.
However, dismantling a 130K engine with still-working tensioners has proved instructive. Both gauze filters in this one were still intact, as expected since the tensioners still worked:
Removing one of the tensioners I think I found not only the reason for the gauze filter in the first place, but also the reason for the filter failure and subsequent tensioner failure - carbon build-up from inside the oil galleries. I didn't get a pic, but underneath the gauze there were tiny chunks of the carbon found in the sump, cam covers etc. As the tensioners have rubber o-rings in them, I think Audi put these filters in to protect them from this carbon, whereas camshafts, crank bearings etc, being metal, wouldn't be affected. The problem though, is that the carbon will eventually accumulate behind this non-replaceable filter which then gets clogged and oil pressure just punches through it. The broken filter material then gets pushed through the tensioner and destroys it.
On balance, I'll take my chances putting the carbon through the tensioner rather than stainless steel mesh, and change the oil more often.
The tensioner pads were in remarkably good condition considering the mileage, but of course I replaced them since everything was in bits
An upside-down engine is oddly satisfying
Its considerably easier to replace the sump like this
Another bonus of having the engine on the stand is that I can take the inlet manifold off with it upside down, thus ensuring none of this detritus falls down the inlet ports:
I have no idea why these engines collect so much grit in this area
Grit removed, sump re-sealed, and back the right way up again. The usual sand and oil mess in here
Better
Hopefully the engine will be complete tomorrow and I can get the gearbox service done on Sunday
