Explaining the Cooling System in Automobiles – Which One is Best?

Almost all cars and some large capacity motorcycles use liquid cooling in their engines. Small capacity motorcycles and aircraft make use of air cooling because they are exposed to the air when travelling. A cooling system in the engine not only keeps the engine cool, at times it keeps the engine temperature at the right level for efficient working of the internal combustion process.

Common cooling system equipment includes a radiator to get rid of excess heat, a fan to force adequate airflow over the fins of the radiator, a thermostat valve that opens or closes depending on the temperature that has to be maintained within the engine, a water pump to circulate coolant throughout the engine and hoses to transfer coolant to and from the engine block.

Air Cooling System in the Engine

In air cooled engine systems, the cylinder walls have external fins that are exposed to the air. As the vehicle moves forward, the air is forced around the cylinder walls and takes away the heat caused by the internal combustion process.

The Amount of Heat That is Dissipated From This System Depends Upon

  •       The surface area of the cylinder’s external metal fins
  •       The rate of airflow which depends on the speed of the vehicle
  •       The temperature gradient between the engine and the atmosphere
  •       The heat conductivity of the metal

Some of the Advantages of Air-cooling Systems in Automobiles Are:

  • Light weight due to the absence of water jackets, water pump, hoses, and radiator
  • Cooling system requires no coolant topping off
  • There are no leaks to look out for
  •  Antifreeze/coolant is not required
  • The engine is able to reach operating temperature faster than a liquid cooled engine
  • Is suitable for use in cold climates where water would otherwise freeze

Water Cooling System

Liquid cooling is another type of cooling system in cars. In this type of system, water is circulated around the cylinder walls, combustion chambers, valve systems and engine block.

The water is kept in motion by means of a water pump that forces the liquid water through the water jackets where it absorbs heat and then towards the radiator where it dissipates heat. The water pump is powered by a V-belt that is attached to the engine crankshaft.

The water is pushed towards a radiator where it is cooled in the radiator fins by means of a fan. The fan and the water pump are driven by the same shaft. The water is then passed into the water pump which forces it back into the water jackets of the engine.

Cooling System Components

The different components that make up the cooling system are as follows:

  • The radiator
  • Thermostat
  • Fan
  • Water Pump
  • Water jackets
  • Coolant/Antifreeze

Advantages of a Water-cooled System in an Engine

  •   The cylinder, cylinder head and valves are subject to uniform cooling
  •   The fuel economy for a water-cooled system is higher than for other types of cooling
  •  With water cooled system, the engine can be placed at the rear of the vehicle
  •  Water cooled engines are less noisy than air cooled engines because the water dampens some of the noise

Disadvantages of a Water-cooled System in an Engine

  • Is reliant on water/coolant/antifreeze for the cooling system.
  • The water pump that is used to circulate water is power hungry and saps a lot of energy from the engine.
  • The water-cooling system should be working at all times otherwise the engine will overheat and get damaged
  • A water-cooled system is expensive because it has a larger number of components.
  • A water-cooled system requires more maintenance.


Internal combustion engines are cooled by two main types of cooling systems : air cooling or water cooling. Air cooling using ambient air that passes over the cylinders and engine to cool the process of internal combustion. Water cooling makes use of a heat exchanger (radiator) to dissipate heat to the atmosphere and a coolant to absorb the heat from the engine.

Air cooling makes use of fins on the cylinder to increase the surface area of the conductive and radiating surfaces. In water cooled systems, the coolant circulates through water jackets and absorbs heat from the cylinders and engine.

Frequently Asked Questions

Q1. What are the 2 types of cooling system?

Ans. In internal combustion engines, air and fuel burn inside the cylinder and produce hot gases. The cooling system is required to reduce the high temperatures and allow the engine to work efficiently. Too much cooling is not desirable as it reduces the thermal efficiency of the internal combustion engine. Not enough cooling and the oil between the moving parts gets burnt and results in seizing or welding of components.

There are two main types of cooling in engines. Air cooling and water cooling. Air-cooling is generally used in small engines up to 20 bhp and in aircraft engines. There is a system of extended surfaces called fins on the exterior surface of the cylinder walls and cylinder head. Heat generated in the combustion cycle is conducted to the fins, and when air flows over them, the heat gets dissipated to the air.

In the water cooling method, water jackets are provided around the cylinder. Water is circulated within these jackets as it absorbs the excess heat created in the cylinders by combustion. The hot water is pumped to the radiator which has a system of thin tubes and a fan used for dissipating heat away. The forward motion of the vehicle also cools the water with air passing over the radiator. The cooled water is then recirculated through the water jackets.

Q2. What are the types of cooling systems?

Ans. The types of cooling systems in cars and automobiles can be either air cooling or water cooling. Air cooling uses air over the surface of the cylinders to cool down the high temperatures caused by internal combustion.

Water cooling makes use of water jackets that surround the cylinder walls and take away heat from the engine and cool it down in a radiator placed at the front of the vehicle.

Q3. What is the function of a cooling system?

Ans. The cooling system has three important functions in the engine. Firstly, it is used to remove excess heat from the engine caused by the internal combustion process. Second, it maintains the temperature of the engine at a constant value at the point where thermal efficiency is maximum, known as the operating temperature of the engine. If it is too cool, the engine is not efficient, and if it is too hot, it may cause damage to the engine components.

Finally, it brings the engine to the right operating temperature once the engine is started. It does this as quickly as possible because it should be at the right operating temperature as the vehicle moves forward.

Q4. What are the five major parts of a cooling system?

Ans. The cooling system is made up of 5 main parts, namely, the radiator, water pump, cooling fan, hoses and thermostat.

The engine produces heat as a result of the internal combustion process of burning fuel and air. This heat is transferred to the engine block and other parts of the engine. The coolant circulates in water jackets surrounding the engine block and cylinder walls as well as the cylinder head. Coolant is circulated throughout the engine by means of the water pump. Hoses carry the coolant around the engine and towards the radiator where it is cooled. The radiator has a fan that forces cool air over thin tubes that circulate the coolant through. The water pump then recirculates the coolant back to the engine where it takes away more heat from the engine.

To maximise the efficiency of the engine, it is designed to warm up quickly. Once the engine reaches the right operating temperature, it is kept stable at this temperature as the engine works. The right engine temperature is maintained by the thermostat. The thermostat works like a valve that opens and closes depending on the temperature. Without the thermostat, the engine would take longer to reach its operating temperature. Once the engine has warmed up to the right temperature, the thermostat regulates flow of coolant to the radiator to cool it down.

Q5. What is the process of a cooling system?

Ans. The cooling system is designed to work by constantly passing coolant through channels known as water jackets in the engine block and then towards the radiator. The water pump is used to force this coolant around the engine block and to the radiator. Heat from the engine is absorbed by the coolant during this process and is dissipated in the radiator.

As the coolant leaves the engine block, it is passed on to the radiator. The radiator has thin tubes that are exposed to the atmosphere and it also has a fan to force air across the tubes. The coolant flows through the thin tubes of the radiator and heat escapes to the atmosphere. The coolant is then sent back to the engine block where it picks up heat and is passed to the radiator again for cooling. This is the cooling process of the engine.

Q6. What are 10 common causes of overheating?

Ans. There are varied reasons why your engine can overheat. Listed are some of the most common causes of overheating

Not enough coolant – Driving the vehicle without the correct level of coolant may cause the engine to overheat. Refill the coolant or antifreeze to the correct level to prevent overheating.

Leaky cooling system – If the coolant system has leaks in the hoses, it can be identified by spots or puddles of leaking coolant below the vehicle.

Faulty water pump – The water pump primary function is to circulate coolant throughout the cooling system. If the coolant is dirty, filled with debris or has too much build-up, then the water pump may be clogged and stop working which leads to overheating of the engine.

Radiator fan – The radiator fan is used to dissipate heat from the coolant. A faulty fan will prevent heat from escaping from the coolant and may increase engine temperatures.

Low Oil levels– The engine oil has two purposes, one is to lubricate the moving parts of the engine and the second is to cool the engine down due to the high heat of friction. A low engine oil level may cause temperatures to rise.

Faulty thermostat – The engine thermostat regulate temperature in the engine by opening and closing a valve to allow coolant to flow to the radiator. A faulty thermostat will cause the engine to overheat because it is unable to maintain the right temperature by sending coolant to the radiator to take away heat.

Belts and hoses – The coolant hoses carry coolant from the engine to the radiator. If they are leaking, bent, blocked or ruptured, coolant will not find its way to the radiator to be cooled. Certain belts are powered by the engine to work the water pump. If the belts are frayed or worn out, the water pump will not be able to circulate water throughout the engine. This may lead to an overheating issue.

Faulty heater core – Coolant will not flow properly if the engine’s heat exchanger is blocked or clogged. This can cause an overheating condition in the engine.

Q7. What happens when the cooling system fails?

Ans. When the cooling system fails it can cause serious or permanent damage to your engine due to overheating. Issues that lead to overheating are mainly related to some block or obstacle that prevents coolant from reaching the radiator to cool down, a faulty thermostat that cannot regulate the temperature, a radiator that has some fault, or a fan / water pump that has malfunctioned. In all these cases, heat from the engine is not dissipated as intended.

If you do not prevent overheating in the engine, it may cause catastrophic damage to the engine permanently. Some of the results of overheating are

Damaged head gaskets – When the engine overheats, it causes damage to the head gaskets between the cylinder head and the engine.

Damaged engine block – Overheating may cause the engine block to crack and get permanently damaged which will be very costly to repair.

Damaged pistons– An engine that is overheating may burn holes or melt pistons causing them to warp. In this case, the whole engine must be disassembled in order to reach the damaged pistons.

Engine seizing – The engine components may seize up due to the excessive amount of heat and weld together, causing catastrophic damage to the engine.

Q8. What are the signs of cars overheating?

Ans. Some of the signs that tell you that your car is overheating are as follows

The temperature or light gauge warning light comes on indicating that the engine is overheating

There is a burning smell coming from the engine, which is most likely the singing or burning of oil, or it could be due to the burning of plastic or rubber components in the engine.

The engine may start to produce ticking noises. This is because the oil is no longer able to lubricate the moving parts of the engine, therefore clearances in the engine will start to tick.

Coolant may escape from the reservoir and may leak onto the ground.

Steam may be seen rising from the coolant reservoir or the radiator cap.

Engine power will be severely reduced as a result of an overheating engine. Pistons will not be able to move smoothly within the cylinders and may cause loss of power.

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