How Does a Car Cooling System Work?

Posted on: June 1, 2016

How Does a Car Cooling System Work?

To explain how a cooling system works, it’s necessary to first explain what it does.  It’s very simple—the cooling system of a car cools the engine.  But cooling that engine can seem like a gigantic task, especially when one considers how much heat a car engine generates.

Think about it.  The engine of a small car traveling at 50 mph on the highway will produce approximately 4000 explosions per minute.  Along with all the friction of the moving parts, that’s a lot of heat to be concentrated in one place.  Without an effective cooling system, the engine would heat up and quit functioning within a few minutes.

The modern cooling system must keep the car cool in ambient temperatures of 115 degrees, as well as keeping it warm in -25 degree winter weather.

Two Types of Cool

There are two types of cooling systems in cars: one is cooled with liquid and the other is cooled with air. Air-cooled engines are almost a thing of the past, and were a trade mark of older Volkswagen Beetles, as well as the Chevy Corvair.

New motorcycles use air cooling, but, in cars, cooling an engine with air is very rare.  Consequently, for the rest of this article we’ll be dealing solely with liquid cooling systems.

What Happens Inside …

A liquid cooling system works by passing liquid continually through the passages in the engine block. Powered by the water pump, the coolant is pushed through the engine block.  As the solutions travels through these passages, it absorbs heat from the engine.

After leaving the engine, this heated liquid travels to the radiator where it is cooled by the air stream entering the grille of the car. The liquid will cool on its travels through the radiator, returning once again to the engine to pick up more of the engine’s heat and carrying it away

There is a thermostat between the engine and the radiator.  The thermostat regulates what happens to the liquid, depending on the temperature. If the liquid’s temperature falls below a certain level, the solution bypasses the radiator and instead is diverted back to the engine block.

The coolant will continue to circulate until it reaches a certain temperature and opens the valve on the thermostat, allowing it to once again travel through the radiator to be cooled.

Because of the extreme heat of the engine, it seems like it would be easy for the coolant to reach a boiling point.  However, the system is pressurized to prevent an occurrence like this. When the system is pressurized, it makes it much more difficult for the coolant to reach a point of boiling.

However, sometimes the pressure builds up and needs to be released before it blows a hose or a gasket.  The radiator cap releases excess pressure and liquid, storing it in a reserve tank.  After the fluid in the reserve tank cools to an acceptable temperature, it’s returned to the cooling system to be circulated once again.

The Killer Cooling Agent: Antifreeze

Antifreeze is an integral part of the cooling system. Composed of ethylene glycol, antifreeze can withstand temperatures tens of degrees below zero, while at the same time without boiling it can handle engine temperatures that exceed 250 degrees.

For most climates, a mixture of 50% antifreeze and 50% water is the best blend for the cooling liquid. If temperatures are much below zero, a mixture of 75% antifreeze and 25% water is best,  but this concentration percentage is the exception and not the norm.

It’s also important to note that antifreeze is highly poisonous to both animals and humans.  Keeping it away from animals is very important, because they are attracted to the sweet taste of the liquid and will readily drink it.  Once it’s ingested, the ethylene glycol forms calcium oxalate crystals, which can cause renal failure followed by death.

So, without trying to sound like the voice of gloom and doom, please be careful with antifreeze, and immediately wipe up any dribbles or spills.

The cooling system can be maintained by completely draining old coolant and replacing it with fresh solution.  A power flush, which must be done by professionals, will clear out any water scale along with any remnants of old coolant or sediment.

One the system is fully flushed in one direction, the mechanic often gives it a reversed flush, going in an opposite direction from the normal flow of the liquid.  After the reverse flush has done its work, a new thermostat is installed, and the system is refilled with fresh cooling solution.

Refilled, descaled, and cleaned, the system is ready to begin again in its work of cooling the engine.