Volks,
I'm trying to pinpoint the cause of a leak -- every now and then I come back
to the bus to find that it's marked its spot (right under driver's side front
cylinder, see photo:
<http://www.offthehill.org/~dan/images/bus/guilty_party.jpg>).
I got a coolant system pressure tester, and hooked it up for the cold and hot
tests (setup photo:
<http://www.offthehill.org/~dan/images/bus/the_setup.jpg>).  Pumped it up to
14.5psi as specified by Bentley; no leakage whatsoever.  Pressure held steady
in three consecutive tests.
When I went to do the hot test, something was amiss: even when the bus reached
operating temperature, the pressure test gauge showed no pressure
(<http://www.offthehill.org/~dan/images/bus/normal_temp_no_pressure>).  I let
it cruise at operating temp for about ten minutes before deciding that I must
be doing something wrong.  As the engine cooled down (coolant was at about
70� C, still no pressure on the guage), I noticed that the test plug was
slowly moving out of the reservoir neck.  Just as my brain registered "RUN!",
I backed away and the thing blew a nice geysir of antifreeze everywhere -- I
was far enough away and was wearing eye protection, so no biggie, but boy is
there a lesson in shop safety there.
So, couple of questions:
1) Am I using the test rig wrong?  There had to have been pressure in the
system.
2) I blew off about a half-liter of coolant.  Do I have to bleed the system,
or can I just top off the main reservoir until it overflows and then cap it?

Many thanks for all your help,
d.
1990 GL -- "Mudskipper"