Hey Karen,

Check your primary coolant tank cap (the black one that has a hose on it).
I suspect that the pressure release valve has gone bad, and the system is
not maintaining pressure.  Coolant is easily pumped out by normal driving.
I had a similar problem on my 84 Audi 5000 S.  The car never overheated
because most of my driving is very short distance with few stops.  But the
temp needle moved around a lot.  I thought it was normal.  Then one day the
car happened to sit at idle for a long time, and suddenly I'm spilling
coolant onto the ground (from the plastic tank).  Replaced the cap, problem
fixed.  Now the temperature gauge is rock steady.  The pressure valve on
the old cap had broken off (it's still bouncing around inside the plastic
tank).

The idiot light on the Vanagon temperature gauge will come on if the
coolant in the primary tank in low (there is a level sensor on top of the
tank).  It is not a temperature alarm, but a coolant level alarm.  I
suspect that coolant sloshes around in your primary tank, causing the
sensor to trip.  I had this happen in my 84 vanagon in the dead of
Wisconsin winter (10 degrees outside).  Car was running only 30 seconds:
the idiot light came on and the needle pegged (almost instantly). Scared me
to death.  Put some coolant in the tank - fixed the problem.  p.s.  I have
a couple of slow head gasket leaks and I had forgot to keep up with the
coolant level. If your heads are dry underneath, I suggest checking out the
cap.  I'd almost bet the bank on it being bad.  The secondary tank level
should be very stable, unless you're running extreme.

Best wishes,

John Hung
84 GL
84 Audi 5000s
86 BMW 325
(three other VWs in my youth)

>What makes the secondary coolent tank overflow on a 1984 Westy?  It
>only does it after cruising on the hwy and then stopping. The heat
>indicator rises at idol, but drops when the fan turns on.   PLEASEEEE
>DON'T 	Head gaskets.
>	Sometimes the light behind the heat gauge comes on.  If I tap the gas
>pedal it goes off. Once or twice upon starting the van the light came on
>and the needle pegged out. I know it was not over heating because it had
>only been running for a few seconds.