Hi folks, I need some help.  I recently bought an 86 westy in good shape
but had cooling problems.  Before I could drive her I had to change the
head gaskets, thermostat housing and 4 bent pushrods.  I did the work my
self and consider the job done correctly.

The problem is...from the first day after the repair, if you let the Van
idle for approx. 15 min., the temperature guage suddenly drops and
occasionally when this happens, the expansion tank bubbles violently.
The engine does not seem to be overheating at this point.  If you turn
off the engine and wait 5 minutes, the guage returns to normal and off I
go.

This does not happen when I am driving the Van.  It only happens while
idleing.  I have put 1800 miles with no problems other then this.  I
have attempted to bleed the cooling system a few times.  I don't know if
I'm doing it incorrectly and trapping air in the system?  Would anyone
agree that the sudden temperature guage dropping is a sign that air has
replaced the fluid surrounding the sensor?  As well as the bubbling in
the expansion tank?

So the question is; Could it be the sensor ( I kind of doubt it
myself)?
                    Is it possible that I sucking air in the system?  ie: vacuum???
                    Is it possible I just don't know how to bleed the cooling system?
(Likely?)
                    Is it possible I screwed up the head gasket job??? (the Vans been
running grear for 1800
                    miles so far)

Any help or suggestions are gratefully appreciated.

Thanks Tony