Most engines operate at roughly 190-210 degrees Fahrenheit, and temperatures inside combustion chambers can reach 4,500 degrees. To keep their cool, engines need a steady and ample supply of coolant (a mixture of antifreeze and water), air and engine oil, plus a well-functioning support team of hoses, a water pump, a radiator and thermostat, plus other components. If any part of the cooling system breaks down, an engine can quickly overheat, causing hot metal parts to warp or even seize from heat and friction. Here are some typical causes of overheating: – Radiators and hoses can develop leaks, so over time there will be too little coolant to circulate throughout the engine and absorb heat. – Radiators can get blocked by plastic bags, dirt and other debris that restricts the flow of air that’s supposed to cool the coolant as it passes through. – Thermostatically controlled fans that draw outside air through the radiator can fail. – A thermostat that’s supposed to open to allow coolant to flow through the radiator may get stuck in the closed position, or the water pump that keeps the coolant flowing around the engine can leak or fail. In either case, the coolant stuck in jackets and passages in the engine will eventually overheat. – A radiator cap that doesn’t seal tightly lowers the boiling point of the coolant, causing an engine to overheat. Most vehicles are supposed to have a 50-50 mix of antifreeze and water, and if there’s too little antifreeze that also lowers the boiling point. Among other problems that can cause overheated engines are failed cylinder head gaskets, which allow coolant to leak into combustion chambers; blocked exhaust systems; “dragging” brakes that don’t release when the pedal is released; and towing or hauling more weight than the cooling system is designed to handle. Though engine oil is not part of the cooling system, it does perform a cooling function by reducing friction between moving parts. In addition, as it gets pumped around the engine it absorbs some heat. An engine that’s low on oil by a couple of quarts or more will run hotter and could eventually overheat.
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