I just read this post from the van archives. (see below)  I'm hoping this is
the source of my leak too. As opposed to it being from the heads. (mine's
leaking from this same general area) Does anyone know if you have to do any
bleeding of the coolant system after you losethe two cups of coolant? Are you
aware of whether this is a potential problem with the '91's as well. I don't
have a manual yet, but I guess I'll have to get one soon.
Thanks in advance for your reply,
David
(yes I tried e-mailing the author re this, but the e-mail address is no longer
correct)

 Coolant Leak Fixed-'85 Westy

     Another note to the list outlining the latest fix.

     I noticed a puddle of coolant directly under the oil filter and began
     tracing the origin.  It is pretty close quarters with all of the hoses,
     connections, waterpump, thermostat housing, etc., but traced it to the
     joint between the pipe that is attached to the head on the pass. side of
     the engine and goes into the waterpump.  The leak was at the waterpump.

     Purchased a new o'ring and gasket for a couple of bucks from the dealer.

     Was anticipating having to drain the coolant so put off doing the work
for
     a few days.  Anyway began by loosening the alternator bracket and then
     removing the steering pump and bracket from the engine(3 bolts) and
moving
     it out of the way(leaving the hoses attached). Pulled two of the belts
out
     of the way to give some working room.  Then removed the two Allen head
     bolts holding the pipe flange to the head.  Some coolant came out(about
two
     cups)but not as much as I thought might.  Then just pulled the pipe out
of
     the hole in the waterpump(after removing the clamp holding the dipstick
     tube to the pipe).  Snaked the pipe all of the way out, cleaned it up,
     replaced the hardened, deformed o'ring and reversed the operation.

     Took maybe 1/2 hour and stopped the leak.

     Pat Spragge