Overheating is caused by anything that leads to a loss of coolant, prevents the cooling system from getting rid of heat, or causes excess heat in the engine itself:

► Coolant leaks (water pump, radiator, heater core, hoses, freeze plugs, head gasket, engine internal).

► Cooling system clogged (deposits built up in radiator or in engine due to maintenance neglect or use of hard water). Use a cleaner, then reverse flush system to clean it out. A badly clogged radiator may need to be rodded out or replaced.

► Weak radiator cap (does not hold rated pressure and allows coolant to boilover). Pressure test the cape to check it out.

► Thermostat stuck shut (replace).

► Inoperative electric cooling fan (check fan motor, relay and temperature switch for correct operation).

► Bad fan clutch (replace if slipping, leaking or loose).

► Missing fan shroud (reduces cooling efficiency of fan).

► Slipping fan belt (tighten or replace).

► Too low or too high a concentration of antifreeze (should be 50/50 for best cooling).

► Bad water pump impeller eroded or loose - replace pump).

► Debris in radiator (remove bugs and dirt).

► Collapsed radiator hose (check lower hose).

► Late ignition timing (reset to specs.)

► Restricted exhaust system (check intake vacuum readings and inspect converter, muffler and pipes).

► Radiator and/or fan undersized for application