Did you verify the actual temperature with a digital thermometer? Maybe your guage is off. I have a 350 in my 48 1 1/2 ton. I plow snow with a 6 ton load of gravel on the back with a stock radiator with a mechanical fan and it never gets over 160 degrees (unless I drive down the road with the plow too high). If it's truely over heating, it's got a blockage somewhere,
Scott
