>>The problem seems to be temperature which at
times runs over 50% and can fluctuate. I've taken my van to three
different Volkswagen dealerships and they check it over and tell me
nothing is wrong with either my cooling system or the engine. It runs
hotter at higher rpms but cools down at lower rpms. I now have about
1,200 miles on  this engine and the temperature gauge can run up to 80%
when I  ride down the freeway on a hot day in the flatlands with the air
conditioning on full blast.

I would check to see if the radiator cooling fan is coming on during hot
engine temps.  The fan should start on low speed when the temp needle is
just above the red light on the instrument panel.  The fan should kick into
high speed when the needle is at about 75 -80 % of the way to the top mark.
Likewise, these come on a little sooner if the air conditioning is on.

If you do not notice the fan working this way, then the problem is likely
the radiator cooling fan thermo switch.  You can find this by taking off
the lower grill and looking for the three wire connector on the right side
of the radiator.  I've replaced 2 of these on my vans.

Good luck, and let us know if this was the case.

Karl
88 GL
86 Westfalia GL