I had the same symptoms and it was my radiator.  The definitive test for me
was running the heater.  The temp would run high until the heater was turned
on with maximum fan speed.  It would then run close to normal.  The problem
was particularly noticeable climbing hills.  A new radiator fixed the
problem.  This was in an 85 7-passenger GL.

Chip

-----Original Message-----
From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com]On Behalf
Of zolo
Sent: Tuesday, August 24, 2004 6:22 PM
To: vanagon@GERRY.VANAGON.COM
Subject: What happens if...

Hi guys,
I was wondering, what happens when the thermostat does not open.  I know
that the engine will overheat, but would the coolant rise in the reserve
tank?  I am experiencing overheating, rising water in there reserve but no
coolant loss or gas in the system.
I don't want to change the radiator if the thermostat is the culprit.
Although the hoses are hot in the front too, which may happen either way.
Now I need someone who knows all these.  Any of you?
I love this list.
Zoltan