Tractor Repair: massey 1020, grass pollen, radiator cap

Question
keeps overheating after about 1 hour of bushhogging.Changed thermostat,tightened fan belt,and replaced rad cap. Don't see bubbles in rad like head gasket is blown. Any Ideas or something I'm missing

Answer
check your radiator, take a hose and rinse it out, sometimes they can get so plugged with dirt, grass pollen ect, they no longer will cool, check to make sure the water pump is circulating, rent or by a coolant pressure tester, the kind that replaces the radiator cap and pressurizes the system allowing you to see if the is a pressure loss somewhere that can cause overheating.