A couple of things to check would be the lower radiator hose - water pump suction can cause a partial collapse of an old hose.
The thermostats also would be suspect, and they're easy to test.
Another thing to check is the air filter. I don't know the grades you're climbing, but I just got back from a trip in my 8 ton motorhome, where it ran a 5-mile, 9% grade at 850°F EGT and 12 psi boost with OAT at 92°F, coolant temp, 215°F. Normal level cruise @ 65 mph is 500°-550°F, boost @ 4.5 psi.
Obviously my engine's different, and the radiator on my diesel pusher is enormous, and other folks with more equivalent trucks can be of more help, but the hose, thermostats, and air filter are pretty generic.
Last edited by rustyk; 07-03-2009 at 20:26.
'94 Barth 28' Breakaway M/H ("StaRV II") diesel pusher: Spartan chassis, aluminum birdcage construction. Peninsular/AMG 6.5L TD (230HP), 18:1, Phazer, non-wastgated turbo, hi-pop injectors, 4L80E (Sun Coast TC & rebuild, M-H Pan), Dana 80 (M-H Cover), Fluidampr, EGT, trans temp, boost gage. Honda EV-4010 gaso genset, furnace, roof air, stove, microwave/convection, 2-dr. 3-way reefer. KVH R5SL Satellite. Cruises 2, sleeps 4, carries 6, and parties 8 (parties 12 - tested).
Stand-ins are an '02 Cadillac Escalade AWD 6.0L and an '06 Toyota Sienna Limited.