Type of cooling system
• Air cooling
• Water cooling
• Thermosyphon system
• Pump circulation system
• Air-cooled engines rely on the
circulation of air directly over hot
parts of the engine to cool them.
• Air cooling works by making the
object to be cooled have a larger
surface area or have an increased
flow of air over its surface, or
• An example of the former is to
add cooling fins to the surface of
• Radiator/pump is absent hence the system is light.
• In case of water cooling system there are leakages, but in this case there are
• Coolant and antifreeze solutions are not required.
• This system can be used in cold climates, where if water is used it may freeze.
• Comparatively it is less efficient.
• It is used in aero planes and motorcycle engines where the engines are
exposed to air directly.
Water cooling system
• Uniform cooling of cylinder, cylinder head and valves.
• Specific fuel consumption of engine improves by using water cooling system.
• If we employ water cooling system, then engine need not be provided at the front end of moving
• Engine is less noisy as compared with air cooled engines, as it has water for damping noise.
• It depends upon the supply of water.
• The water pump which circulates water absorbs considerable power.
• If the water cooling system fails then it will result in severe damage of engine.
• The water cooling system is costlier as it has more number of parts. Also it requires more maintenance
and care for its parts.
• Thermosyphon is based on natural convection, which
circulates a fluid without the necessity of a mechanical
• Convective movement of the liquid starts when liquid in the
loop is heated, causing it to expand and become less dense,
and thus more buoyant than the cooler liquid in the bottom
of the loop.
• Convection moves the heated liquid upwards in the system
as it is simultaneously replaced by cooler liquid returning
• Ideally, the liquid flows easily because a good
thermosiphon should have very little hydraulic resistance.
• Cheap as no water pump is required.
• Reliable as there are no moving parts.
• Circulation of water depends solely on engine temperature. The hotter the
engine, the greater is the circulation.
• In order to achieve efficient circulation, the radiator top tank must be well
above the engine.
• Cooled water enters the engine at the bottom of the cylinder, where the
engine normally runs fairly cool and it heats up to maximum as it reaches
the top of the cylinders. Therefore, it has a reduced cooling effect on the
hottest part of the engine.
• Difficult to fit an interior heater successfully without a water pump.
• Under conditions of very heavy load or in hot climates the water may not
circulate as quickly as required.
Pump circulation system
• Now you will see how car cooling system works by
sending a liquid coolant through passages in the engine
block and heads.
• As the coolant flows through these passages, it picks up
heat from the engine. The heated coolant then passes
through a rubber hose to the top inlet of the radiator in
front of the car.
• The coolant flows down through the thin tubes in the
radiator; the hot coolant is cooled by the air stream
entering the engine compartment from the grill in front of
• Once the coolant has made its way to the bottom of the
radiator and is cooled it returns to the engine through a
rubber hose to absorb more heat.
• The water pump has the job of keeping the
fluid moving through the entire system.
Cooling System Components
• Radiator: Many radiators are mounted at
the front of the vehicle in the path of
greatest airflow. The air carries heat
away, cooling the liquid before it returns
to absorb more heat from the engine.
• Coolant hoses: Cooling system hoses are
flexible to allow for movement, and
molded to fit the shape needed. Most
hoses are made of rubber, and reinforced
with a layer of fabric.
Cooling System Components
• Water-Pump : The water pump pumps
coolant through the engine and radiator. It
is belt-driven from a pulley. A hose
connects it to the bottom of the radiator.
• Thermostat: A thermostat shortens an
engine's warming-up period. It is a valve
operated by coolant temperature. It stops
coolant circulating through the system
while the engine is cold.
Cooling System Components
• Cooling-fans: A fan helps generate
airflow through a radiator. It can be
driven either by a belt off the crankshaft,
or electrically. It can be controlled
according to temperature.
• Radiator-pressure-cap: One way to help
prevent a coolant boiling is to use a
radiator pressure cap that uses pressure
to change the temperature at which
• In western countries if the water used in the radiator freezes because
of cold climates, then ice formed has more volume and produces
cracks in the cylinder blocks, pipes, and radiator.
• So, to prevent freezing antifreeze mixtures or solutions are added in
the cooling water.
• Anti-freeze solutions are mixed with water in different proportions
according to the expected temperature.
• The lower the temperature, the higher the percentage of anti-freeze
solution necessary to avoid freezing.
• The ideal antifreeze solutions should have the following properties :
• It should dissolve in water easily.
• It should not evaporate.
• It should not deposit any foreign matter in cooling system.
• It should not have any harmful effect on any part of cooling system.
• It should be cheap and easily available.
• It should not corrode the system.
No single antifreeze satisfies all the requirements.
• Normally following are used as antifreeze solutions :
• Methyl, ethyl and isopropyl alcohols.
• A solution of alcohol and water.
• Ethylene Glycol.
• A solution of water and Ethylene Glycol.
• Glycerin along with water, etc.
Troubles and remedies of cooling system
• Overheating: Improper coolant level, Wrong Thermostat, Bad water pump, Radiator internal
• Overcooling: Faulty thermostat
• Loss of Coolant: Check Leakage in Hoses, Gasket, Seals & cracked wall
• Improper Cooling Fan Operation: Check Battery Supply & Connections, switch or fan relay not