I'd check the Vanagon archives - there is a copy of an excellent article
from "Import Service" about head replacement. In the first paragraph,
there is an excellent description of the symptoms of a leaking head.

You can see it at:
ftp://gerry.vanagon.com/pub/technical/HeadGasketProcedure/

Also, while talking with my Mechanic, he showed me how sometimes the
ends of the plastic coolant hoses will have the end-rings break loose
and block the flow of coolant. Interestingly the way he checks for a
blocked cooling system is by using a spot-temperature gun at the
radiator to check for cool spots.

I guess the definitive test would be to get the van warmed up and
immediately do a leakdown test.

Todd
'88 leaky Westy