How a vehicle cooling system works

08 June 2021

In short, the engine must have heat in order to function properly and prevent any early wear to your vehicle’s engine. However, too much heat can have the opposite effect and therefore could end up costing you for the damage.

Vehicle Engine

What you need to know:

The cooling system works by transferring the heat from the engine, across to the coolant or antifreeze. This will then travel to the radiator and the excess heat will be lost to the outside environment. After this, the coolant will travel back to the engine where the process will start again. However, there are many parts to a cooling system which play a part in the process.

Cooling system parts


Coolant/ anti-freeze.

Water pump.



Radiator fan.

The radiator

The radiator sits at the front of a car, and as stated earlier, it transfers the heat from the cooling system to the outside environment. It offers a design that features flat fins that are connected to flat tubes to make a square or rectangular shape that sits behind the front grill of a vehicle.

NOTE: You should never remove the radiator cap when the engine is hot as the system is pressurised and therefore can fizz and cause personal injury.

Coolant/ antifreeze

Coolant is also known as antifreeze. It is the fluid that regulates an engines temperature and stops it from freezing, even in extremely cold conditions.

Typically, coolant is a 50/50 mix of both ethylene glycol and water and should be replaced based on the vehicle’s manufacturer recommendations in order to protect parts of the cooling system from corroding, as well as the engine freezing in cold temperatures.

Water pump

You will find that on many vehicles, the water pump can be found nearby or underneath the timing belt. It is functioned by either a timing belt/ chain or a serpentine belt which is connected to the pumps pulley. Both the belt/ chain and the pulley turn the blades/ vanes to create a suction that constantly keeps the coolant/ antifreeze circulating.

It is important to check for any leaks in your vehicles water pump, as they often fail due to leaks.


A vehicles thermostat sits between the engine and the radiator. It is usually connected to the upper and lower radiator hose and opens and closes to allow or prevent coolant/ antifreeze flowing to the radiator.


The rubber hoses are used for coolant/ antifreeze to travel to and from the engine to the radiator. However, due to there exposure, they can weaken with time as well as age.

Radiator fan

Sometimes a vehicle can have one or more radiator fan. It is the part which helps transfer the heat to the outside air (as explained in the radiator section) and makes it flow across the radiator.

The fan is controlled differently on both older and newer vehicles.