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How Does Your Engine’s Cooling System Work?

engine cooling system serviceThere’s a lot that your engine has to do in order to keep you moving. It’s taking fuel from the fuel system and creating tiny, controlled explosions. Components are turning, spinning, and cranking and with all that is involved, the engine gets pretty hot rather quickly. In fact, the typical engine operates between 195 to 220 degrees Fahrenheit and that doesn’t even include ambient temperatures! In the summer it gets even hotter in there. Luckily, your engine has the ability to keep its cool with the use of a radiator and other components as part of the cooling system. So, how does a car engine cooling system work?

Cooling System Components 

The cooling system is made up of several components and passages all through the engine block and heads to keep the engine cool. Still, none of these components would be able to perform their tasks without the use of coolant. A mixture of chemicals and water, coolant, also referred to as antifreeze, keeps the engine cool as well as keeps the engine water from freezing in lower temperatures. Coolant also has some additives including lubricants to help protect the engine from damages. Coolant begins at the water pump and travels through the engine’s passages collecting heat as it goes. It flows to the cylinder heads to collect heat from the combustion chambers, flows past the thermostat, through the radiator hose, and into the radiator. The coolant flows through the fins of the radiator where it is cooled by the airflow traveling through the radiator. Once it leaves the radiator, it returns to the water pump through the lower radiator hose. 

Water Pump

Driven by the serpentine belt from the crankshaft, the water pump’s job is to ensure the coolant moves continuously through the engine, radiator, and hoses all while maintaining an ideal temperature. Without a functioning water pump, the coolant will not be able to travel to where it is needed to remove the heat and can cause the engine to overheat.


Liquid-cooled engines are equipped with a thermostat that is located between the engine and the radiator. The thermostat monitors the coolant’s temperature and regulates its flow. The thermostat monitors the temperature of the engine and if the temperature of the engine is cold, the thermostat prevents the coolant from flowing and is directed back to the engine. As temperatures climb, the thermostat will slowly begin to open. The thermostat will fully open once the engine reaches a temperature of around 200 degrees Fahrenheit.  


The radiator is a heat exchanger meant to transfer heat from the coolant through its passages so that the coolant can continue traveling through the engine. Mainly made from aluminum, radiators transfer heat from the hot coolant through tubes and as air blows with the assistance of fans, it blows across the fins of the radiator to cool the fluid.

Radiator Cap  

Water boils at approximately 212 degrees Fahrenheit and since coolant is made up partly of water, it too will boil at 212 degrees, right? Not quite. Thanks to the pressure created by the radiator cap, the boiling point is raised considerably. However, too much pressure can cause severe damages and some pressure must be released. The radiator cap releases pressure once it reaches a certain point. 


There’s only one way for coolant to travel around your engine and that is through the radiator hoses. Hoses are flexible connections attached to the engine that transport coolant between the engine, radiator, and everywhere in between. The coolant is directed to the radiator for cooling and is returned back to the engine. The job of the heater hose is to direct coolant to the vehicle’s heating unit, called the heater core, to keep interior temperatures warm in colder months.

The Importance of the Engine’s Cooling System

Your engine functions better at warmer temperatures but too much heat can be detrimental to an engine. Serious damages could occur to the engine that may be irreversible and lead to replacement or very costly repairs. When any part of the cooling system breaks down, your engine is vulnerable to heat damage. Components in and around the engine are in danger of exposure to intense heat. Overheating can cause seals, sensors, belts, and other components to melt. In the case where the thermostat is faulty, where the coolant is present but unable to circulate, that can cause overheating that may also cause severe damages. Hoses that are under pressure, for example, can cause the coolant to boil, creating significant pressure, and expand which could cause hoses to burst and leak coolant. 

Cylinder heads sit above the cylinders on the cylinder block and close the cylinder to create the combustion chamber. Cylinder heads, though, are made of aluminum and not meant to withstand severe temperatures. By allowing the car to overheat, the cylinder heads can begin to melt and warp. Warping is troublesome as it affects the combustion process and may lead to a decrease in the engine’s power, cause misfires, or oil leaks. 

An overheating engine can also cause the head gasket to blow. The damaging effects of a blown head gasket are significant and costly. Coolant begins leaking and winds up mixing with the engine oil. While both fluids are ideal for your vehicle’s function, they do not work well together. Oil and coolant cause poor engine performance and affect the exhaust system including causing smoke to pour out of the exhaust. 

What Does the Engine Cooling System Light Mean?

When the temperature gauge in your car reaches the “danger zone,” the red area closest to the ‘H’ for hot, a light that looks like a thermometer with waves, indicates that the engine is getting too hot and may overheat. This is an indication to you to find a safe place to pull over and attempt to get your engine to cool down. If you’re in traffic and you begin to notice the needle climbing upwards, you can attempt to reverse the heat by rolling down your windows and turning the heater on high. In any case though, if your car begins to overheat, do not attempt to drive any further. Do not risk the potential damage to your engine. Instead, contact a towing service and have your vehicle towed to your favorite neighborhood automotive center where a technician can determine what is causing your vehicle to overheat.