Always these machinations to remove the air from the Vanagon coolant system.
Spending days in the hope that the internal aeration of the coolant will
eventually result in all that air being burped into the atmosphere through
the pressure cap; jacking up the front end; jacking up the rear end; hooking
up pumps; etc., etc., etc.  If the purging of air from a closed system were
such an arduous and unpredictable task, then Chernobyl would be a weekly
occurrence and thousands with hot water heat would die of hypothermia every
time the winter wind blew through Gary, IN.

ALL that is necessary is to vent ALL the highest points (starting at the
lowest, of course) in the system while filling from a constant supply of
coolant.  It is that simple.  You will have heat, your engine will thank you
and many attendant problems will go away.  I have a feeling that most of the
head failures result from cooling systems which are not totally airless.  No
air pocket, no localized overheating.  Also, without oxygen aluminum tends
not to corrode.

Rich