[s-cars] Help with problem oil leak - long

[Dave Ellis]

Hey fellow S-listers,

I had my '93 S4 in the shop last week for a slew of work (timing belt 
change with all the works, new suspension - Eiback Pro with Boge 
TurboGas, etc.).   One item of particular interest was to have a 
persistant and fairly large oil leak (a 250ml per day Mobil1 habit) 
corrected by replacing the crank seal which was deemed by everyone 
involved to be the culprit.

Anyways, after picking up the car it seemed the oil was leaking just as 
much (although the car handled *much* better, but that's another post) 
and that the culrpit had not been the crank seal after all.  Oil is 
still dripping off the oil pump housing and blowing back onto the 
downpipe and other hot bits, and I still can't see exactly where the 
oil is leaking from.

The oil only leaks with the car running, slowly at 2 bar and somewhat 
more at 5 bar, and for a short while after the engine has shut down.  
Oil pressure continues to be good however, 5 bar when driving and 2 bar 
at idle.  It is not leaking from the bolts holding the timing belt 
idler/tensioner pulley onto the block, and though the leak is getting 
the crank seal and crank bolt very oily, it is apparently not the crank 
seal.  

I have not been driving the car much for the past six months because of 
the leak, but now that I'm selling my A4 and moving to one car I need 
to get this resolved.

Some photos I took of the leak last fall are linked below.  The photos 
take place over the period of about one minute and show the oil leaking 
over the freshly cleaned front bottom of the engine (actually the oil 
pump):

  http://pictureposter.audiworld.com/54496/oilleak-img_1869.jpg
  http://pictureposter.audiworld.com/54496/oilleak-img_1870.jpg
  http://pictureposter.audiworld.com/54496/oilleak-img_1871.jpg
  http://pictureposter.audiworld.com/54496/oilleak-img_1872.jpg
  http://pictureposter.audiworld.com/54496/oilleak-img_1874.jpg

My mechanic beleives that it could possibly be the oil pump gasket, or a 
cracked oil pump.  I concur, but It's also occured to me that it could 
be a leak in the oil pan gasket or a had gasket leak.  The difficulty 
is that the source of the leak is hidden.

What does the collective wisdom of the list have to say?

Thanks!
-Dave

'93 S4
'99.5 A4 1.8t (soon to be sold)