Overheating of internal combustion engines has been around as long as engines themselves. Along with creating torque and power for propulsion, heat is a co-product of combustion. Cooling systems, air or liquid, are intended to remove heat from the engine at nearly the same rate as it is rejected from the engine. Cooling systems fail. Water pumps, thermostats, drive belts, hoses, clamps and gaskets all fall victim to gradual or sudden failure which results in engine overheating.

Everyone even slightly familiar with engines is also familiar with overheating, it is, quite possibly, the single most frequent type of engine failure. Automobile instrumentation will invariably include some sort of overheating indicator, a temperature gage or indicator light. Ignore these and the problem will not just go away, it will get worse, and ultimately engine failure will result.

Automotive overheating is usually the result of a cooling system component problem, examples are shown below:

• Coolant - insufficient level indicating a leak in the system
• Water pump - failure of pump or drive belt
• Thermostat - stuck closed
• Radiator - blocked airflow, fouled water passages or defective cap.

Certain unfavorable conditions can lead to overheating as well. Pulling a trailer up a hill using the air conditioning on a hot day can overtax the cooling system and result in overheating despite that the cooling system is in good order. Idling on a hot day can lead to overheating because of lack of airflow past the radiator and low coolant flow.

Despite the best efforts of automotive engineers to provide an adequately sized, well designed and instrumented cooling systems, costly problems manage to occur. The driver must recognize the problem and take steps to correct it. Gauges and indicator lights are sometimes ignored, this can lead to catastrophic engine failure. Cylinder heads break, crack or warp; valve springs lose their "temper" and will fracture shortly thereafter; engine components, wiring and hoses melt.