Important Water Cooling Parts of Internal Combustion Engine | What is the Importance of a Cooling System in a Car

Cooling System:

01- Engine Cooling system - Engine Water cooling system

Automobile engines produce heat during the power stroke, so the heat is transferred to all the parts of the engines. In order to prevent the overheating of the engine, a cooling system must be included. The functions of the cooling systems are:

  • Keeping the engine temperatures below normal temperature (i.e. 80 degree Celsius below)
  • Transferring the heat from the combustion chamber to all the part of the engine, so that the engine can work better
  • Preventing the Engine from Overheat

Methods of Engine Cooling:

  • Air cooling
  • Water cooling

Normally Air cooling used it for two wheelers while Water cooling used for four wheelers and above.

Air cooling

01- Two wheeler Engine air cooling system

01-Engine water cooling system - Antifreeze

Water cooling

Merits and Demerits of Air cooling over Water cooling:


  • Comparatively lighter due to absence of Radiator, Cooling jackets and Coolant
  • Can be operated in extreme climates, where water may freeze
  • Definite advantage in areas where there is scarcity of water
  • Easier maintenance since there is no leakage problem
  • Earlier warming up than water cooled engines


  • Not easy to maintain even cooling all around the cylinder, More cooling obtained in multi cylinder engines
  • Less efficient Heat transfer
  • Fan absorbs larger engine power
  • More noisy due to absence of water around cylinders, which acts as sound insulator
  • Some engine components may become inaccessible, leading to difficult maintenance

Components of Water Cooling System:

  • Radiator
  • Pressure cap
  • Expansion reservoir
  • Thermostat
  • Pump
  • Fan


A component of the engine cooling system, which is in fact a heat exchanger. Its function is to dissipate the engine heat from the coolant to the atmosphere. Parts of the radiator are:

  • Upper tank
  • Lower tank
  • Radiator core
  • Radiator fin


Upper tank holds the hot water / Coolant from the engine, Lower tank holds coolant which sent back to engine, radiator core which connects upper tank and lower tank, were the number of cores depends on the cooling power required for the engine and finally radiator fin made up of thin zinc formed over the cores, while the air contacting over the surface removes heat from the radiators

Pressure cap or Radiator cap:

The pressure cap not only act as a lid, it has a pressure regulating mechanism. It has a spring that pushes the valve downwards. In normal position due to the spring pressure it holds the valve, so the valve is closed. When the pressure inside the radiator increases which makes the valve open.

01- Pressure cap - Radiator cap


Thermostat is a part that have function like valve. This valve will close and open the port between water jacket and high temperature radiator hose. It works to speed up the engine to get the working temperature.


Thermostat works with close and opening the channel of water jacket to the output channel in the radiator hose. When the engine temperature is low, thermostat is fully closed. That makes closed coolant circulation inside the water jacket. This circulation will faster engine temperature increasing, because heat from combustion chamber is circulate by coolant in all of engine part.

But when the working engine temperature reached (± 80 degrees C ) thermostat will slowly open. And the coolant automatically circulated outside to the radiator. The thermostat works automatically by utilizing a special wax that reacts to the temperature that affects it. But some thermostat using electric motor to open and close the valve.

Types of Thermostat:

  • Bellows or Aneroid type
  • Wax or Hydrostatic type

Cooling fan

The cooling fan works to take down the radiator temperatures. The working principle of cooling fan is by flowing the air from outside through radiator fins. There are two kinds of  cooling fan, i.e.

01 - Radaitor cooling fans

  • Conventional Cooling Fan, the working of this type is following the engine. So when the engine running on low RPM, the fan will rotating on low RPM too. This is happened because, the fan driven by engine pulley by v belt.
  • Electric cooling fan, second type there is more efficient fan. The electric fan work by electric current that flow through motor fan. The fan work only when the coolant temperature above the engine working temperatures.

Methods of power saving in Cooling Fan:

  • Variable pitch fan blades, which may be speed – sensitive or temperature – sensitive
  • Fan driven through a fluid coupling, where the spacing between rotors is controlled by the coolant temperature
  • Fan driven by separate electric motor controlled by thermostat in the cooling system

Water pump

The water pump is only have one function, i.e. to circulate the coolant in order to move inside the cooling channel. The water pump is generally located inside the water jacket, when the thermostat closes this pump will cause a water flow in the water jacket that helps flatten the engine heat.


When the thermostat is open, there are coolant flow from the water jacket to the radiator for decrease its temperature. Same with cooling fan, there are two type of water pump. Conventional versions driven by engine power and electric versions powered by electric current.


A chemical, such as Alcohol or Glycerine, added to the engine coolant, to lower its freezing point

01 - Anti freeze engine cooling - coolant

Anti-Freeze solution requirements:

  • Should be thoroughly miscible with water
  • Should not have any corrosive action on system components
  • High boiling point
  • Should not deposit any foreign matter in the jackets, hose pipes or radiator core
  • High specific heat capacity, comparable to that of coolant
  • Should not be inflammable
  • Viscosity not excessive
  • Readily miscible with corrosion inhibitor and anti-scaling compounds

Temperature Gauge:

  • Bourdon tube type
  • Electricity operated type

01-bourdon tube gauge

01-Electrically operated Temperature gauge - Thermocouple

Cooling system troubles:

  • Overheating
  • Slow warm up
  • Noisy coolant pump

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