I just watched my 87 syncro Westfalia being winched onto a flat bed tow
truck for the 3rd time in 5 months near Bend Oregon this weekend, all
three times were the result of catastrophic failure of the main
crankshaft oil seal. I am appealing to the list now to solicit some more
ideas about what could be wrong before I drive back to Bend (from
Portland, Oregon) next weekend to try and fix it.  The first time this
happened was on a trip to NWT in Canada.  That time it was the part of
the seal that contacts the flywheel that ripped.  The next time the
break was on the face of the seal (hence the hypothesis that the seal
had been rubbing on the flywheel  (although it did not appear to stick
out - the replacement was very well countersunk), of course I don't yet
know where it has failed this time.  I do however know from looking back
through receipts from the previous owner that this 40k engine has now
had 6 main seal failures in its life.  My current hypothesis from
talking to mechanics at VW is that there is something wrong with the
flywheel (it looked OK but I did not check the diameter of the sealing
surface) so I have a freshly machined replacement from AVP to replace it
with.  Needless to say the O ring was replaced each of the last 2 times
and I also checked the end play last time which appeared to be well
within limits (I will measure it again when I dismantle it next
weekend).

Both the last two times the symptoms have started as soon as the engine
was reinstalled.  Oil leaked from arround the bell housing from day one
after replacing the oil seal.  Not a huge amount but enough to spot the
rear door after freeway driving and leave a daily oil mark on the
driveway.  This suggests that the seal is under some sort of stress
right from the start. Then after about 2000 miles the seal fails
completely and all the oil drains out. I guess if the flywheel diameter
was too small it could cause a leak but why the seal then fails
completely I dont know. I am wondering if there is anything that could
cause the oil pressure to be too high in this area (faulty instalation
of bearings??).  Or does anyone have any other ideas - I am at a loss
now and if it starts to leak again after I replace it this time I will
have to replace the engine.  Unexpected catastrophic failure of the oil
seal is just not something I can live with (it makes me shudder to think
of some of the places I have been where this could have happened).  All
ideas gratefully received!
David