Cooling System of IC Engine: Definition, Types, Advantages, Disadvantages, Necessity [Notes with PDF]

This is a complete guide on the Cooling System of Internal Combustion Engine. In this article, First, we will see the definition of engine cooling system then types along with advantages, disadvantages, and necessity of the engine cooling system.

Let’s assume a typical 4 cylinder vehicle cruising along the highway at around 50 miles per hour, will produce 4000 controlled explosions per minute inside the engine as the spark plugs ignite the fuel in each cylinder to propel the vehicle down the road. 

These explosions produce an enormous amount of heat and if not controlled, will destroy an engine in a matter of minutes. Controlling these high-temperature heat is the job of the cooling system.

What is the Engine Cooling System?

The Engine cooling system is one of the necessary thing that is present in the Internal Combustion Engine to reduce the temperature of the components inside the engine. It also helps to reduce the wear out of the component and provide smooth functioning and long life of the components.

What are the Types of Engine Cooling Systems?

Generally, there are two types of the cooling system, and those are:

  • Air Cooling System
  • Water  Cooling System

So let’s discuss these types broadly.

Air Cooling system:

In this system, the heat from the engine is directly dissipated to the atmosphere.

The Basic Principle of this type of system is to allow a flow of current through the parts from which heat is to be dissipated, which depends upon the surface area of metal in contact rate of flow of air, a temperature difference between hot surface and air. 

And Surface area of metal will be increased by providing the fins around the cylinder which is made of copper or steel.

engine air-cooling system
Air-Cooling System, Learn Mechanical

Advantages of Air Cooling System:

These 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 Cooling System:

Air Cooling System also has some disadvantages, and those are:

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

Examples of Air Cooled Engine:

  • It is used in scooters, motorcycles, and tractor. 

Water Cooling System:

This type is the most commonly used type of system.

In this system dissipation of heat is done by the circulation of water through the jackets around the cylinder and passes this hot water through the radiator where air absorbs heat from the water.

There are two types of water cooling system. 

  1. Thermosyphon
  2. Pump circulation system

Thermosyphon System:

The pump is not fitted in this system.

Circulation of water is done due to the difference in densities between hot and cold water.

However, in this cooling system, the rate of cooling is low. Nowadays its usage is limited because we need to maintain the water to a certain level.

It is simple in construction and cheap.

diagram of Thermosyphon System
Diagram of Thermosyphon System, Learn Mechanical
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 and,

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 causing 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 and travels down from the upper tank to the lower tank, and rejecting heat as it travels.

This cooled water from the lower tank is passed into the cylinder water jacket and hence circulated again for the process.

The limitation of this system is that this cooling depends only on temperature and is independent of engine speed.

Pump Circulation System:

In this cooling system, the circulation of water is done by providing a centrifugal pump.

Due to this pump, the rate of flow of water is more.

Here radiator may be fitted at any place convenient to the designer.

The pump is driven by a belt from a crankshaft.

diagram of pump circulation cooling system
Diagram of Pump Circulation Cooling System, Learn Mechanical
Working of Pump Circulation System:

In this system, the direction of cooling water flow is upward from the cylinder head to the top tank of the radiator, then down through the radiator core to the bottom tank.

From the bottom tank,  it moves through the lower radiator hose to the cylinder block water jackets by the help of the water pump, which circulates the water.

Water enters the engine at the center of the inlet side of the pump.

The circulating pump is driven by a belt from the crankshaft.

As engine speed increases, the flow of coolant increases.

Parts of the Water Cooling System:

These are some major parts of water cooling system:

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

Let me explain all.


Radiator is a heat exchanger used in a IC Engine, it consist of two tanks [oner is called upper tank, and other one is lower tank] and buch of tubes connected to the both tanks.

The upper tank is connected with the exit channel of engine jackets via hose pipe, and bottom tank is connected with the entry channel of the cooling jacket via a water pump.

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

In general radiators are made of these metarials:

  • Cast iron
  • Mild steel
  • Stainless steel
  • Aluminium
  • Copper
  • Brass
Water Pump:

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


Fan is used for blowing the air through the radiator tubes. It is driven by the same belt which drive the pump.

Water Jackets:

It is fitted outside the engine cylinder. These jackets are used for trasffering the heat fromt he engine cylinder.

Hose Pipe:

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

Thermostat Valve:

The function of this valve is to restrict the flow of water from the engine to the radiator. This valve design as when the water temperature inside the engine cylinder exceeds a certain value (Generally 70-degree centigrade) then the valve allows the flow of water, if the temperature of the water inside the cylinder is below 70-degree centigrade then the valve restrict the flow of water.

main parts of water cooling system
Parts of Water Cooling System, Learn Mechanical

Advantages of Water Cooling System:

These are some advantages of Water Cooling System:

  • In these 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 vapourization so that e=the efficiency of water cooling is more.

Disadvantages of Water Cooling System:

The disadvantages of Water Cooling System is mentioned below:

  • Some time corrosion occurs inside the radiator or pipe or storage.
  • Due to scaling heat transfer rate is goes down after the long run, so it needs regular cleaning and maintenance.

Examples of Water Cooled Engine:

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

Necessity of Cooling System:

The need of cooling system in an IC Engine because of the following reason:

  • During the operation of an engine, the temperature inside the engine can go up to 2500 degree centigrade (Source: How Stuff Works), which is above the melting point of the components used to make the engine. So we need to use the cooling system to dissipate the heat as much as possible.
  • As we know, we also need lubrication system to the proper functioning of the engine, but due to the high heat, the property of lubricating oil can be changed. That result seized of the engine. So to avoid that we need to use a cooling system.
  • Sometimes due to the enormous heat, thermal stress in built-up inside the engine, so to minimize the stress we need to keep the engine temperature as low as possible.

A Video on How Engine Cooling System Works?

So this is all about Engine Cooling System, I hope you liked this article and learn something new from this stuff. If you appreciate our work do share this article on your favourite social media platform. See you on some another article, till then enjoy the rest of your day, work hard, learn new things, and be happy always. Cheers!

More Resources:


  • All Images are made by Saubhik Roy- Design Team Learn Mechanical
  • Feature Image: Modified by Author
  • Video By Autotechlabs


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Anup Kumar Dey

A Mechanical Engineer with 19 years of working experience in various renowned MNCs.

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