The van runs hot (3/4) sometimes and then quite suddenly it will run normal (1/2),
for a few days before just as suddenly running hot again for a while.  The
change always comes suddenly, while driving.  The overflow tank is high when
it runs cooler and goes down again as the engine cools after shutdown.  When
it is running hot the overflow tank level does not rise at all, or fall when shutdown.

Anyone know whats going on?

Maybe the cap is faulty?  Any idea how this might work?

TIA
--
A. Miguel Calvin
mcalvin@ican.net
Guelph, Ontario, Canada
83.5 1.9l Westy