Engine Cooling System: How it Works

01/08/2022 12:00AM

The main function of an engine’s cooling system is to ensure the engine operates at its optimum operating temperature. An automotive engine operates best at the temperature predetermined by the manufacturer. When an engine operates below the set/targeted temperature, component life is reduced, emits more pollutants, and the engine becomes less efficient. Therefore, the important task of the cooling system is to allow the engine to come up to operating temperature as quickly as possible, and then maintain a constant engine temperature. The engine cooling system is made up from four key components the Radiator, Water Pump, Thermostat, and a Fan. These components all work together to bring the engine up to the operating/set temperature as quickly as possible, and then maintain it.


Radiators are usually manufactured from aluminium, copper, or brass. They are made up of many small diameter tubes with fins attached. Notwithstanding the materials used, radiators are basically of two types: crossflow and down-flow radiators, depending on where the tank is located. These designs allow the radiator to exchange the hot engine coolant temperature with the ambient air, with the assistance of the cooling fan thus reducing coolant temperature before it re-enters the engine.

Water Pump:

The mechanical water pump circulates the coolant from the radiator through the cylinder block, heater core, and cylinder head. Eventually, the hot engine coolant enters the radiator again and allows the radiator to cool its temperature. Mechanical water pumps are mostly driven by the engine, they can also be replaced by an Electric Water Pump (EWP®) to improve cooling performance and efficiency.  


The Thermostat is a temperature-controlled valve that only allows coolant to pass through the radiator at the manufacturer’s set/targeted temperature. When the Thermostat is closed, it redirects the coolant through a by-pass passage to recirculate the coolant through the engine which assists to bring the engine up to operating temperature more quickly. The Thermostat is a crucial component within the cooling system and should not be removed unless you are converting to a Davies Craig EWP® with a Digital Controller. Without a Thermostat or a Digital Controller installed to regulate engine temperature, the results may be low coolant temperatures, longer warm up times and can lead to overheating. 

Cooling Fan:

The performance of the radiator is heavily dependent on airflow. A Davies Craig cooling fan is used to supply airflow to the radiator when the ram-air produced by the moving vehicle is not sufficient. In modern vehicles, the cooling fans are typically electric but previously the fan was from the mechanical water pump The mechanical belt-driven fan is regularly removed and replaced with a Thematic Electric Fan to free up engine power and improve cooling performance.