Engine Cooling System: Types, Definition, Working, Parts, FAQ’s [PDF]

Before we delve into the IC Engine’s cooling system, imagine a standard 4-cylinder vehicle cruising at 50 mph on the highway. Inside the engine, the spark plugs ignite the fuel in each cylinder, creating 4000 controlled explosions per minute to propel the vehicle. These explosions generate heat. This could break down the engine within minutes. Its role is to manage and control the excessive heat.

What is an Engine Cooling System?

An Engine cooling system is one of the necessary systems that are present in the Internal Combustion Engine to reduce the temperature of the components inside the engine. It also helps to reduce the wear and tear of the component. It also helps in the smooth functioning and long life of the components.

What is Engine Cooling System?

Functions of an Engine Cooling System

Following are the functions of an engine cooling system:

  • Regulating the engine temperature
  • Reducing engine wear and tear
  • Prevents overheating
  • Prevents damage to engine
  • Improves the engine performance

Types of Engine Cooling Systems

The following are the two main types of Engine Cooling Systems:

  • Air Cooled Engine Cooling System
  • Water Cooled Engine Cooling System

Air Cooled system

In an air cooling system, the engine’s heat is released directly into the surrounding air. This system involves current flowing through the parts that need heat dissipation. This process depends on many factors. This includes metal’s surface area in contact, the air’s flow rate, and the temperature difference between the hot surface and the air. To enhance the metal’s surface area, fins made of materials like copper or steel are added around the cylinder.

Air Cooled system diagram

Advantages of Air Cooled System

Following are some advantages of using Air Cooling System:

  • Light in weight
  • No antifreeze is required
  • This system can be used where water scarcity is there
  • Simple in design
  • Require less space
  • No tapping up of water, etc.

Disadvantages of Air Cooed System

Following are some disadvantages of using Air Cooling System:

  • More noise in operation.
  • The coefficient of heat transfer of air is less, hence less efficient in working.

Examples of Air Cooled Engine

Air cooling systems are generally used in the following vehicle engines:

  • Scooters
  • Motorcycles
  • Tractors

Water Cooling System

This is the most commonly used type of system. In this system, the dissipation of heat is done by the circulation of water through the jackets around the cylinder and then this hot water is passed through the radiator where the air absorbs heat from the water.

Water Cooled system diagram

Classification of Water Cooled System

Water cooling system is further classified into two main types: 

  • Thermosyphon
  • Pump circulation system
Thermosyphon System

There is no pump included in Thermosyphon system. Circulation of water is done due to the difference in densities of hot and cold water. An important point to note here is that in this cooling system the rate of cooling is low. It is simple in design and cheap.

Thermosyphon System
Working of Thermosyphon System

The thermosyphon cooling system operates on the principle of natural convec­tion. Thermo-syphon water cooling system is based on the fact that water becomes light on heating. The top and bottom of the radiator are connected to the top and bottom of the cylinder water jacket respectively with the help of pipes. The radiator is cooled by allowing air to flow over it.

Airflow is achieved by vehicle motion or a fan provided. The heated water inside the cylinder water jacket becomes light and moves out of the upper connection pipe into the radiator. It then travels down from the upper tank to the lower tank rejecting heat as it travels. This cooled water from the lower tank is passed on to the cylinder water jacket and hence circulated again for the process. The limitation of this system is that cooling depends only on temperature and is independent of engine speed.

Pump Circulation System

In this type of cooling system, the circulation of water is done by providing a centrifugal pump. Due to the presence of pump in the system, the rate of flow of water is more. Radiator may be fitted at any place that is convenient to the designer. The pump is driven by a belt attached to the crankshaft.

Pump Circulation System
Working of Pump Circulation System

In this system, the direction of cooling water is upward starting from the cylinder head to the top of the radiator, then down through the radiator core to the bottom tank. From the bottom tank,  it moves through the lower radiator hose up to the cylinder block water jackets with the help of the water pump. The circulating pump is driven by a belt from the crankshaft. As engine speed increases, the flow of coolant also increases.

Parts of the Water Cooled Engine Cooling System

Following are some main parts of a water cooling system:

  • Radiator
  • Water Pump
  • Fan
  • Water Jackets around the Cylinders
  • Hose Pipe
  • Thermostat Valve

A radiator is a heat exchanger used in an IC Engine. It consists of two tanks. One is called an upper tank, and the other one is a lower tank. A bunch of tubes are connected to both tanks. The upper tank is connected to the exit channel of the engine jackets via a hose pipe, and the bottom tank is connected to the entry channel of the cooling jacket via a water pump.

The hot water comes from the engine cylinder filled in the upper tank. From the upper tank, the hot water comes to the lower tank with the help of radiator tubes. By the time of flowing through the tubes, the hot water is cooled by atmospheric air or sometimes a fan is fitted at the back of the radiator.

What are Radiators of Water Cooled system made of?

In general radiators are made of the following materials

  • Cast iron
  • Mild steel
  • Stainless steel
  • Aluminum
  • Copper
  • Brass

Water Pump

Water pump is used for forced circulation of water inside the engine. The water pump is driven by a belt which is connected to the crankshaft.


The fan is used for blowing the air through the radiator tubes. It is driven by the same belt which drives the pump.

Water Jackets

It is fitted outside the engine cylinder. These water jackets are used for transferring the heat from the engine cylinder.

Hose Pipe

It is the pipe connected between the engine’s water jackets and the radiator.

Thermostat Valve

A thermostat valve’s role is to control the water flow between the engine and the radiator. Its design allows water to flow within the engine cylinder. This happens at a specific temperature which is around 70 degrees. When the cylinder’s water temperature falls below this threshold, the valve restricts the flow.

parts of water cooled system

Advantages of Water Cooled System

Following are some advantages of Water Cooling System:

  • In this types of cooling, we see a high heat transfer rate.
  • This type of cooling system is used where the size or power of the engine is more.
  • Thermal Conductivity is more
  • Water is easily available
  • Liquid has a high enthalpy of vaporization so that the efficiency of water cooling is more.

Disadvantages of Water Cooled System

The disadvantages of Water Cooling System are mentioned below:

  • Some time corrosion takes place inside the radiator pipe or storage.
  • Due to scaling, heat transfer rate goes down after the long run, because of which it needs regular cleaning and maintenance.

Examples of Water Cooled Engine

All the modern engines (Cars, Bus, Trucks, etc.) nowadays use this type of cooling system.

Why is Engine Cooling System necessary?

The following are the reasons why there is a need of cooling system in an IC Engine

  • Engine temperatures can reach up to 2500 degrees Celsius, exceeding component melting points (source: How Stuff Works).
  • A cooling system is required to dissipate this heat effectively.
  • High temperatures affects the properties of lubricating oil.
  • A cooling system is essential for maintaining lubrication integrity.
  • Excessive heat can result in thermal stresses within the engine.
  • Controlling temperature is vital to minimize these stresses.

A Video on How Engine Cooling System Works?


The Cooling system of an IC Engine is responsible for removing access heat generated due to combustion preventing the engine from overheating and minimizing the risk of damage to components.

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