9 Cooling System Parts and Function in Your Car

The cooling system parts work together to ensure that the engine always has the right temperature. Knowing every aspect of the cooling system parts and function is essential.

Knowing the engine cooling components will make it easier to point out any damaged part and repair it.

In this article, we will look at the 4 functions of a car cooling system. We will also look at the various parts of a cooling system.

cooling system parts

4 Functions of Car Cooling System

The cooling system serves four essential functions, which include the following.

1. Reduce the temperature of the engine

The primary function of the cooling system is to remove excess heat from the engine system. By doing this, the engine cannot reach a dangerous temperature for its parts.

The cooling system will release coolants when the engine reaches 195 to 220 degrees Fahrenheit. At this point, the coolant steps in to remove excess heat and brings the engine temperature down.

The thermostat will slowly close when the engine reaches average working temperature, stopping coolants from circulating.

2. Reduce the temperature of the lubricant

You must know that the lubricant in your engine also performs cooling functions. It collects heat from the engine surface as it circulates through the engine.

In collecting it from the engine, the oil gets very hot and can cook up the lubricant, increasing oil consumption and other problems.

The cooling system ensures that the lubricant does not get too hot to the extent that it starts cooking up.

3. Maintains a constant engine temperature

With the help of the various cooling system components, the engine temperature is adequately managed. Features like the radiator fan will work once the engine temperature hits about degrees Fahrenheit.

Once the cooling system is activated, the engine’s temperature runs at about average working temperature.

4. Brings the engine to working temperature

Also, the cooling system ensures that the engine temperature rises to a working temperature quickly. How does it do this?

The engine is usually cold, especially in the morning. When you start the engine, the thermostat isolates the engine from the radiator. The thermostat is a valve that controls the coolant flow to the engine.

By isolating the engine from the radiator, the engine’s temperature can rise quickly. Without this happening, the engine will not gain heat fast enough because it loses it to the radiator.

Cooling System Parts and Function

There are a lot of cooling system components, and they each play important roles. The component does everything from cooling the vehicle to ensuring that the engine is warm and stays at working temperature.

Below are some of the component cooling systems.

1. Radiator

Car Radiator

A radiator is an integral part of cooling system that stores and disperses coolants, antifreeze, and water.

The radiator functions byusing three significant parts: the outlet, inlet pressure cap, and core. Each of these parts plays an independent role within the radiator.

Radiator works with the help of the hoses to connect it to other parts of the cooling system. With this connection, the coolants can quickly get to important parts of the engine that it is needed. 

2. Thermostat

The thermostat valve opens and closes in response to the engine coolant’s temperature. It works in connection with the radiator.

Thermostat Valve

A thermostat opens when the coolant temperature reaches between 180 and 195 degrees Fahrenheit. Once the thermostat senses this temperature, it will open up and allow coolants from the radiator to flow to the engine, which will cool the engine.

The thermostat will remain closed if the engine is not hot enough. It allows the engine to warm itself up.

Also, the thermostat works with the water pump, as the valve regulates the movement of the coolant aided by the water pressure.

3. Cooling fan

Car Cooling Fan

The function of the cooling fan is to reduce the coolant’s temperature. After the coolant has circulated through the engine and collected, it is returned to the radiator.

Once the coolant is in the radiator, it is usually very hot and needs to be cooled down. It is when the cooling fan comes in. It creates airflow to the radiator, which then cools the fluid.

The cooling fan is controlled by the Engine Control Module (ECU). The ECU uses temperature sensors which send reading that it uses to start the cooling fan.

4. Hoses

Radiator Hose Pipe

The hose is what makes circulation possible. The hose will carry the coolant from the radiator to the engine and return the coolant to the radiator.

There are two significant types of radiator hoses: the upper and lower ones. The lower radiator hose carries the cold coolant from the radiator to the engine.

On the other hand, the upper radiator hose is responsible for carrying the hot coolant from the engine back to the radiator.

5. Freeze plugs

The freeze plug, also known as the core plug, protects the engine from damage from the cold. They are cylindrical shaped plugs that fill up spaces in the engine created for the sand cores.

This engine cooling system component occupies the passages where the removal of casting sands is in the engine. The plug ensures that there is no leak of oil coming from the passage.

Although the freeze plug can last hundreds of thousands of miles, you must check them to ensure they are not damaged.  

6. Heater core

An advantage of the hot coolant from the engine is that it is handy for the vehicle’s interior. Car manufacturers designed a heater core to use the heat from the hot coolant.

The heater core is connected to a rubber hose which collects the hot coolant from the water pump and then returns it to the top of the engine.

A fan is present, which blows the heater core and sends heat from the hot coolant interior of the vehicle.

7. Pressure cap and reserve tank

The reserve tank is now designed specially to be a pressure cap. It keeps the coolant flowing as the pressure cap expands.

A pressure cap keeps the pressure in the cooling system intact when the coolant is flowing. The cap has a spring valve which will let out some pressure if it is in excess.

8. Water pump

The water pump is responsible for the coolant flow through the engine. It creates the necessary pressure to push the coolant through the engine system. It can do this by releasing water pressure.

Water Pump

The water pump is found at the front of the engine and will keep coolant flowing until it returns to the radiator.

9. Bypass system

The thermostat uses temperature to open and close, which could be a disadvantage. In some cases, the coolant in the engine is not hot enough to open the thermostat. It is when the bypass system comes in.

A bypass system will allow the coolant to bypass the thermostat and radiator to return to the engine. In the engine, the coolant can achieve the temperature it needs to open the thermostat.

How does a Car Cooling System Work?

The car cooling system operates as a coherent unit, with each part playing a critical role in maintaining the engine’s optimum operating temperature. Here’s a step-by-step explanation of how a typical liquid-based (water-cooled) car cooling system works:

Step 1: Starting the Engine

Upon starting the engine, it begins to generate heat due to the combustion process happening inside the cylinders. This heat needs to be regulated to prevent engine overheating and ensure smooth performance.

Step 2: Thermostat Remains Closed

Initially, the thermostat remains closed, allowing the engine to warm up quickly to its optimal operating temperature. During this phase, the coolant circulates only within the engine.

Step 3: Circulation of Coolant

As the engine reaches the optimal temperature, the thermostat opens, allowing the coolant (a mixture of water and antifreeze) to circulate from the engine to the radiator.

Step 4: Water Pump

The water pump plays a vital role in this phase. Driven by the engine, usually via a serpentine belt, it circulates the coolant throughout the cooling system.

Step 5: Radiator

The hot coolant flows from the engine to the radiator, a device equipped with many small tubes and fins designed to dissipate heat. As the coolant passes through the radiator, it loses its heat to the atmosphere, aided by the cooling fans, especially when the car is stationary or moving at low speeds.

Step 6: Heat Absorption

The now-cooled coolant returns to the engine, where it absorbs the excess heat generated by the engine, preventing it from overheating.

Step 7: Heater Core

Parallelly, part of the hot coolant flows through the heater core. When you turn on the car’s heater, the air is passed over the heater core, using the heat from the coolant to warm the cabin of the vehicle.

Step 8: Coolant Reservoir

The cooling system also includes a coolant reservoir or expansion tank, which compensates for the coolant’s expansion and contraction due to temperature changes, ensuring that the cooling system remains filled to the correct level.

Step 9: Monitoring by Sensors

Throughout this process, the temperature sensors continuously monitor the temperature of the coolant and engine. The information is displayed on the temperature gauge on the car’s dashboard, alerting the driver if the engine starts to overheat.

Step 10: Cycle Repeats

This entire process is cyclical, with the coolant continuously circulating, absorbing, and dissipating heat, thus maintaining the engine at the right operating temperature.

Car Cooling System YouTube

In summary, a car’s cooling system works harmoniously through a series of controlled stages, constantly managing the engine’s temperature to prevent overheating and ensuring efficient operation.


Now that you have seen the major coolant system parts, you can understand how broad its components are. It is why it could be tricky to find the cause of a failed cooling system. However, you can fix cooling system issues with the right tools and knowledge.

Akindayini Temiloluwa

I am Akindayini Temiloluwa, an automotive expert writer and car enthusiast. I have over three years of experience in the automotive writing niche and have completed over 300 pieces of content from 50 projects. I have vast knowledge and skill in vehicle repairing, all mechanical work, car upgrades and maintenance. My goal as an automotive content writer is to simplify the most challenging concepts for my readers, help them self-diagnose what may be wrong with their vehicles and offer real value for their time.

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