What Causes Your Car’s Engine To Overheat?

By Lawrence Reaves

Automotive engines are designed to withstand a high operating temperature. Most vehicles built over the past fifteen years operate within a range between 200 and 240 degrees Fahrenheit. But beyond the upper limit, the assembly will overheat, potentially sustaining major damage. Continuing to drive your car once the temp gauge on your dash spikes could literally destroy your engine.

There are several elements that can contribute to overheating. It is important to be familiar with them so you can diagnose the problem in the event it occurs. Below, we’ll first describe the issues an overheating engine can cause. We’ll then discuss some of the factors that may be involved.

What Happens When Your Engine Overheats?

Numerous problems can occur once an engine overheats. First, the head gasket can fail. The gasket is sandwiched between the cylinder head and engine block, both of which expand as the engine’s operating temperature rises. The head and block are made from different metals, and thus expand at different rates. The gasket may be crushed under severe pressure.

Second, spark knock can occur. This is a knocking sound that indicates that the fuel inside one or more cylinders is detonating rather than being ignited by the spark plug. With time, it can damage the pistons and rod bearings.

Third, a severe overheating problem can impair the cooling system. The coolant that normally transfers heat away from the engine to the radiator may becomes so hot that the hoses carrying the fluid may rupture. A sizable rupture can starve the assembly of coolant, and likely cause it to seize.


Most overheating problems are due to issues inside the vehicle’s cooling system, or parts that affect the system. We’ll start with the head gasket.

Bad Head Gasket Seal

We mentioned earlier that the head gasket is positioned between the cylinder head and engine block. One of its responsibilities is to provide a seal that prevents coolant from entering the cylinders. If this seal becomes compromised, coolant may leak inside, reducing the level of fluid flowing through the cooling system. Since less fluid will be available to transfer heat away from the engine, overheating can occur.

Failing Water Pump

The water pump’s main job is to keep coolant moving between the radiator and engine. If the pump stops working, the flow of coolant will be cut off, causing the engine to overheat. This can occur in a couple ways.

First, the pump is equipped with blades – they are usually made from plastic or metal – that turn in order to circulate coolant through the component. These blades can wear down and break, impairing coolant flow.

Second, the shaft seal may develop a leak. A leak will allow coolant to seep outward, lowering the amount available to the engine.

Coolant Leaks

Thus far, we have highlighted two potential sources of coolant leaks: the head gasket and water pump. But the fluid can leak from several other sites. For example, the hoses carrying the fluid can crack or rupture under pressure. The attachment points between the hoses and radiator may also develop leaks. Cracks in the engine block may allow coolant to drip into the cylinders.

If you suspect fluid is escaping your car’s cooling system, have a mechanic pressure test the entire system to identify the source. Then, have it fixed as quickly as possible.

Radiator Failure

The radiator is designed with small passages. Coolant flows through them, and releases heat absorbed from the engine. Due to rust, corrosion, and various debris that accumulates over time, these passages may become partially blocked. Additionally, the vents through which heat is normally released may become plugged by dirt and insects; the radiator’s position near the front of the car exposes it to these elements.

If coolant is unable to release heat, it will be unable to absorb more from the engine. As a result, the assembly can overheat.

Take note of any problems that develop in the areas above. Realize that small issues tend to worsen if they are neglected, and can place your engine at risk. It pays to have them resolved as soon as they surface.

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