Ron,
The Cat, Detroit, Cummins engines in those mountain climbing busses also
have a 5 to 10 gallon coolant capacity, plus a water cooled oil cooler.

And the radiator's are all 4 core monster's.

Also, they only turn 1900 to 2100 rpm. and they have big cubes, with
mega horsepower compared to the Vanagon's.

This all adds up to why they don't overheat going over the mountains,
not just the placement of the radiator.

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Terry--
74 Campmobile- (Clementine)
85 GL- (Delilah)
86 BMW 325 ES- (Eva)