Maybe I should ask a very binary question on this issue ... should the ram air across the radiator at 85 mph in 80F weather maintain the minimum temp of the thermostat with the air conditioner on?

Sounds like some believe this is the case ... if so, then neither the viscous clutch nor either electric fan should have anything to do with the increased temperature "profile," right?

Ergo, it is either the thermostat not passing enough coolant, or the radiator not cooling enough coolant, or the pump not pumping enough coolant, right? So, as I replaced the pump (not likely this is an issue since it looks and is geared the same as the one I took off), only the radiator and tstat could be the issue, right?

__________________
George Stephenson
1991 350 SDL (200K and she ain't bent, yet)
former 2002 E320 4Matic Wagon - good car
former 1985 300 CD - great car
former 1981 300 TD - good car
former 1972 280 SEL - not so good car
a couple of those diesel Rabbits ...40-45 mpg