Engine cooling systems and overheating

Have you ever been driving down the road on a hot summer day and thought to yourself “boy do I feel sorry for my engine”. Most motorists probably don’t experience these emotions but I know I did until I learned more about how an engine cooling system works and that it was specifically designed to make my engine feel better on a hot summer day.

Picture of car radiator

Internal combustion engines generate a tremendous amount of heat this is just a fact of life that needs to be dealt with in the design stage of automotive development. This is why even a vehicle that does not have a visible grille will have some kind of method to throw air through the radiator while the vehicle is traveling down the road or sitting still at a stoplight.

The heat from the engine is created when the fuel is ignited inside the combustion chamber of each cylinder. Combustion chamber temperatures can run extremely high. They can approach 1000°F. If it wasn’t for the engine cooling system internal parts like the Pistons, valves and cylinder walls would eventually melt.


It is the job of the engine cooling system to remove this heat before damage is done. In the automotive world there are actually two ways to get this done. The first method which is not used often except by Volkswagen and a few other select automotive and motorcycle companies would be air cooling. But in most cases you find some type of liquid cooled system.

Liquid engine cooling systems

Picture how a car radiator works

It’s really not that complicated and hear is how it works. In short a heat absorbing liquid that we will call engine coolant is circulating inside the engine. This liquid is pumped through the engine and after absorbing the heat of combustion is directed toward the radiator which is a heat transfer device.

A vehicle’s radiator transfers the heat of the engine coolant to the air flowing through it via highly conductive metal fins. The engine coolant is then returned to the block by some type of water pump to repeat the cycle. The engine cooling systems are pressurized in most cases to about 15 pounds per square inch so that the boiling of the liquid will not occur.

The boiling point is also pushed up by the mixture of the anti-freeze. This is why you should not just add plain water. On the other hand you also need to check that the engine coolant that you are adding does contain the proper amount of water. When you go into your auto parts store sometimes they have coolant available that needs to be mixed 50-50 with water.


Water will boil at 212°F and will freeze at 32°F. When you add a mixture of anti freeze you will raise the boiling point to about 230° and can lower the freezing point to subzero temperatures. The proper mixture of engine coolant is so important that I recommend buying pre-mixed to make sure that you get this right.

Another thing to consider is the brand or type that is installed in your automobile many vehicles today offer different types of extended life engine coolants. While older automobiles still have the ethylene glycol-based type, which is most commonly green in color. Note that many engine coolants are poisonous and need to be handled with care and kept out of the reach of pets and children.

Make sure you check your owner’s manual before topping off the coolant reservoir. You really do not want to mix different kinds of engine coolant because it can reduce the efficiency of the heat removal. Another thing to check in your owner’s manual would be this service intervals or the replacement of the engine coolant.

Even extended life fluids most often recommend complete replacement at the 100,000 mile mark. Vehicles with the older type coolant usually recommend replacement at around 30,000 miles. Before you approve a coolant flush at your local quick change oil center make sure that they not only got the recommendation right but are installing the right kind of replacement fluid.

For more articles about how the automobile works this next link will take you to the homepage for the blog about auto repair. I also have another site that is more technical or advanced and supplies my recommended resources for learning car repair.

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