Engine

Low coolant, air in the cooling system, stuck thermostat, no thermostat, Bad hoses, bad water pump, Dirty corroded heavy deposits in radiator, radiator cap not sealing good, Water only no anti-freeze, A Catalytic Converter or exhaust clogged/plugged, Radiator fans not working, Low oil level, clogged oil galleys, air foil not in place between the radiator and engine directing air flow, Leaking head gaskets, exhaust in coolant, timing off, running too rich, trans cooler in radiator and trans is running hot, leaks else-where in cooling system, something blocking air flow threw radiator, poor running engine.