I will be taking the van in to a local independant VW shop for diagnosis
Friday, I think, for the excess coolant showing up in the fill tank.  This is
what I will ask for.  Correct me if I am wrong about, or have missed anything.

1. Test for exhaust gasses in the coolant.  If yes, compression test
cylinders to determine which head is leaking.  Could heads need re-torquing?
Any opinions on whether this would mean scrapping the long-planned family
vacation that we are supposed to leave for on Monday? (1400 miles round trip
from Washington DC to NC mountains).

2.  If no exhaust gasses, then check radiator cap (new with engine rebuild 3
months ago).   Cap is holding at least *some* pressure, ie, when remove hose
fro cap, no squirt, when unscrew cap I get overflow.  Also, it does suck back
at least some of the time.

3.  If no bad cap, pressure test cooling system and look for leaks.  Any
prime candidates here?  The engine compartment bleeder valve?  Water Pump
housing?  I had lots of new rubber put on with the new engine, I think the
radiator is 7 or 8 years old.

One thing I know of in the cooling system of this van, is that on the
previous engine, the flange or housing that the water pump connects to was
machined down too far years ago.  When the new engine was installed, and the
housing moved over, it was too short for the bolts, and the shop bolixed up
the water pump installing it, and I had to buy a second one.  They
successfully installed that one using shorter bolts. Could this be the source
of the air in the system?

Note, there does not seem to be any coolant leaking, just air coming into the
system and forcing coolant into the fill tank.

Sorry to take so much bandwith up with this, but I am distressed about this
and only have a few days to figure it out.
Peter & Zippy