What pressure rating does the radiator cap have? Every pound of pressure on the cooling system raises the boiling point 3 degrees at sea level. A 15 pound cap keeps the coolant from boiling all the way to 257 degrees, and as long as the coolant is liquid, it's still moving heat from the engine to the radiator. If the engine doesn't go above 200 on a hard uphill pull, it sounds like you're OK. If you want to run a lower coolant temperature consistently, you're going to need a bigger radiator or move more air volume over the one you've got. You could also install a restrictor washer in the thermostat housing to slow down the coolant flow- - - -it might not be spending enough time in the radiator to get cooled adequately before going back to the engine to pick up more heat. Use a laser temp gun to evaluate the efficiency of the radiator- - - -aim the gun at the inlet and outlet nipples of the radiator to see how much heat is actually getting transferred to the cooling air. The results might surprise you.
Jerry
