I've got a problem with my 87 Westy that has both I and my mechanic 
stumped. He keeps grumbling something about those wonderful aircooled engines.
Right now "Fru Pedersen" my 87 Westy isn't running right. Upon freeway 
driving at about 65 mph or when loading the engine on a uphill climb my 
coolant temp rises ( measured at 207 degrees F.). This is not good. Runs 
fine going downhill. We just bled the system and replaced the thermostat 
(80 degree C. one). The waterpump is 1� years old, works fine. New heads 
and gaskets on both sides 11 months ago, total 88,000 miles on her. About 
35 days ago we replaced the original muffler which was very "airy" with a 
new one.
Interestingly enough this problem developed after the Westy was parked for 
5 days. Ran fine before then, but upon my return July 5th, and starting her 
up, the temp would climb to near the top of the guage as described above. 
I'm not losing any coolant. Engine runs fine good power, it just runs hot 
when going uphill or flat out on say Highway 101 from Santa Rosa to SF 9 
days ago. We are both stumped, and my mechanic ( although mostly an 
aircooled guy) has been working on VW's for 25 years.

  Anybody have any suggestions or help ?

Interestingly enough I have a 89 Jeep Cherokee that is also experiencing 
the exact same symptoms. It was parked next to Fru Pederson . Perhaps it's 
a virus going around ?
Thanks

Hans-Peter Elmer