How Does an Engine Keep Its Cool? Key Components of an Engine Cooling System

How Does An Engine Keep Its Cool

Herndon, Virginia – Everybody understands that a car overheating is a bad thing. Not only is it inconvenient, but overheating can lead to major engine damage. It can also be dangerous. Overheating can leave you stranded on the freeway. Steam pressurized in the cooling system can leave you badly burned. Engine fires have been known to occur. Overheating is bad. But did you know that an engine that runs too cool can present problems of its own?

The engine in your car, truck, or SUV is supposed to get hot. In fact, it has no choice. The combustion process, along with friction created by all the moving parts, produces a lot of heat in the engine, even on cool days. So the engine block heats up. And that’s a good thing. If it did not, the engine would fail to run at peak performance levels. Premature engine component wear would occur. And exhaust emissions, pollution, would rise.

The engine in most vehicles is designed to operate somewhere between 195 and 220 degrees Fahrenheit for optimum performance. The cooling system regulates the engine temperature to make sure it stays within its appropriate range. But how does the cooling system work? And how can a vehicle owner make sure that it keeps working?

How does an engine cooling system work?

In order for an engine to stay cool, engine coolant (also known as antifreeze for its ability to withstand freezing) is circulated through passages inside the engine block where it absorbs heat by way of conduction. The warmed coolant then leaves the engine and carries the heat with it, allowing the engine to cool. For this cooling process to happen, several components need to function properly. The radiator, coolant hoses, water pump, thermostat, expansion tank, and heater core are all integral parts of the engine cooling system.

Once the coolant draws heat out of the engine, it passes through an upper coolant hose (or “radiator hose”) on its way to the radiator. The radiator is a series of narrow pipes through which the heated coolant passes. These pipes are woven through a matrix of wafer-thin aluminum ribbons (or “fins”) that absorb the heat through the pipes, from the coolant. Air passing through the radiator draws the heat away by means of convection. The cooling fan helps to move a higher volume of air through the radiator. The coolant temperature drops and the coolant cycles back to the engine through the lower hose.

The water pump is the component that forces the coolant through the system. If the water pump is not working properly, the coolant will not flow and the engine will overheat. The water pump is driven by either the serpentine drive belt, or by the engine timing belt.

If coolant is allowed to circulate constantly, the engine will be unable to reach a high enough temperature to work properly. So the coolant flow must be controlled. The thermostat is a valve that is tasked with regulating the flow of coolant. It remains closed until the engine reaches its maximum operating temperature. Then the thermostat opens to allow circulation until the engine drops to to its minimum operating temperature. A faulty thermostat is a common cause of overheating problems.

A couple other components are also at play in the cooling system. The coolant expansion tank, sometimes referred to as the overflow bottle, keeps the car from losing coolant when its temperature rises over its boiling point. The heater core is not directly part of, but is attached to the cooling system. Some of the heated coolant is diverted to the heater core (something like a small radiator) located beneath the dashboard. A fan blows through the heater core and transfers heat to the passenger compartment to warm the occupants on cool days.

How can overheating be prevented?

The component of the cooling system you are most likely to come in contact with is the coolant, or antifreeze itself. Typically made from ethylene glycol mixed with water, coolant comes in concentrated form (must be mixed 50/50 with water) or ready-to-use. The system should stay full of coolant. You can easily monitor the coolant level by looking at the expansion tank. There is usually a high- and low-level indicator on the side of the bottle. If the level is low, you can add coolant, either into the expansion tank or directly into the radiator (exactly where coolant is added depends on the vehicle make and model – check your owner’s manual for recommendations). And keep an eye open for coolant leaking on the ground.

Not all engine coolant is the same. It is essential to check the vehicle manufacturer’s recommendations to make sure you use the proper coolant. Care must also be taken any time the radiator cap is removed. The radiator cap should never be removed when the engine is hot to the touch. Make sure the engine is allowed to cool and the upper radiator hose is free from pressure before removing the cap. Serious burns from scalding can occur otherwise.

But the best way to make sure your cooling system is in proper working condition is to have it inspected by a professional technician as part of regular and routine maintenance, or any time a related component needs to be serviced. (For instance, if the timing belt needs to be replaced, the water pump should be replaced also). Let the qualified technicians at Hogan & Sons Tire and Auto make a thorough assessment of the cooling system next time you have your car in for service.


This article is intended only as a general guidance document and relying on its material is at your sole risk. By using this general guidance document, you agree to defend, indemnify and hold harmless Hogan & Sons Tire and Auto and its affiliates from and against any and all claims, damages, costs and expenses, including attorneys’ fees, arising from or related to your use of this guidance document. To the extent fully permissible under applicable law, Hogan & Sons Tire and Auto makes no representations or warranties of any kind, express or implied, as to the information, content, or materials included in this document. This reservation of rights is intended to be only as broad and inclusive as is permitted by the laws of your State of residence.

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