How a vehicle cooling system works

When up against hot summer temperatures, we’re all trying to keep our cool. But did you know that without a cooling system, your car’s engine can also overheat and even fail completely? 

Let’s go over what this system does, what parts it relies on, and a step-by-step breakdown of how it works. 

how a vehicle cooling system works - Fonctionnement du système de refroidissement d’un véhicule

What is the cooling system for?

The engine cooling system has three important jobs:

  1. To remove unwanted heat from the engine. 
  2. To bring the engine to a comfortable operating temperature as quickly as possible. 
  3. To maintain an efficient operating temperature, by raising the engine’s temperature in cold weather or lowering it in the heat. 

In a modern-day vehicle’s engine, the combustion chambers produce heat in temperatures over 2200°C, but only roughly a third of this heat is needed to power the vehicle. The rest of the heat needs to be removed or else the engine will fail. One third leaves with the exhaust gases and the final third is siphoned out by the cooling system. 

There are two basic types of cooling systems: air cooling systems and liquid cooling systems. Because air cooling systems are generally reserved for small one- and two-cylinder engines, we’ll focus on the liquid cooling system. 

Cooling system parts

The liquid cooling system uses coolant and relies on many parts to keep your engine at the right temperature:

  • Cooling jacket: made up of cylinder ducts filled with coolant, situated around the engine cylinders. 
  • Water pump: circulates the coolant in the cooling jacket in a closed loop. 
  • Radiator: cools liquid with a high-efficiency heat exchange process. 
  • Cooling fan: attached to the radiator to assist with cooling liquid. 
  • Coolant temperature sensor: triggers the cooling fan(s) to turn on when a certain temperature is reached. 
  • Radiator cap: funnels coolant in and out of the expansion tank to manage pressure. 
  • Expansion tank: holds coolant and has space for liquid expansion. 
  • Thermostat: divides the cooling system into two circuits to increase efficiency and reduce engine wear. 

These parts are located directly in and around the vehicle’s engine. Some systems may have additional parts, changing the way the system works, but its purpose is always to remove excess heat from the engine to keep the car running smoothly. 

How it works

Let’s break down the basic steps to how the cooling system keeps your engine at a stable operating temperature. 

Getting started

The cooling system starts with the cooling jacket, which removes heat from the engine. A water pump helps circulate the coolant with a centrifugal pump, which is rotated by the belt drive and powered by the crankshaft. Cooling liquid with special properties, such as anti-corrosion, anti-cavitation, and non-freezing, is required for this system. However, this process moves too slowly to work on its own, so the engine can still easily overheat. 

Cue the radiator. The radiator has two tanks: one with an inlet pipe for hot liquid, and another with an outlet pipe for cool liquid. Fins and tubes connect the two tanks, which work together as the radiator core. 

If things are still too hot, the coolant temperature sensor will turn the radiator fan(s) on. This device also displays the coolant temperature on your dashboard. 

Managing pressure

The engine cooling system is a closed/sealed system. As the temperature within the system increases, the coolant expands, increasing the pressure in the system. This brings the coolant to a higher boiling point, but any excess pressure must be released to avoid damage. 

When the maximum pressure is reached, the radiator cap opens to let coolant escape into the expansion tank. The expansion tank cap helps relieve pressure by releasing and drawing in air. When the pressure decreases again, the coolant is drawn from the expansion tank back into the cooling system. 

Increasing efficiency

To make this system more energy efficient, a thermostat divides it into two circuits. The longer of the two circuits involves the radiator whereas the shorter one bypasses it.

When the coolant temperature is low, the shorter circuit is used so the engine can reach its operating temperature faster. Once the coolant temperature passes 82°C, the thermostat valve starts to open, mixing the hot and cold liquid together to balance the temperature. If the temperature continues to increase past 93°C, the thermostat will shut off the shorter circuit and rely only on the longer circuit.

With these parts working in unison, your engine can maintain a stable operating temperature, even on those hot summer days.

Warming and cooling the cabin

A final essential part of the engine cooling system is the heater core. This is where the engine cooling system intersects with the cabin A/C system. 

The heater core takes the heat generated by the coolant and uses it to warm the vehicle’s cabin in the winter. During summer, the engine cooling system is crucial to the A/C system because the A/C relies on a functioning engine to work. 

To learn more about how the A/C system works, check out this article. 

Cooling the battery

Your car’s battery also needs to keep cool to properly power the vehicle. If the engine cooling system isn’t working, the battery can also overheat. Neglecting battery maintenance and exposing the vehicle to extreme weather are other common causes for battery overheating. Check out this article for more information about how heat affects your car’s battery. 

For any questions about your vehicle’s cooling system or to find materials for your next DIY project, visit a NAPA Auto Parts store to speak with an expert. 

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