The document discusses engine cooling systems. It describes how cooling systems work to maintain optimal engine temperature, prevent overheating, and allow for efficient operation. There are two main types of cooling systems - air cooled and liquid cooled. Air cooled systems rely on fins and airflow over cylinders to dissipate heat, while liquid cooled systems circulate coolant through the engine and radiator to absorb and dissipate heat. Key components of liquid cooled systems include water jackets, water pumps, fans, radiators, hoses, thermostats, and coolant mixtures. Proper cooling is important to prevent damage and allow engines to perform as designed.

1. Cooling System
•Get the engine up to optimum operating Temperature as
quickly as possible and maintains it at that temperature.
•Controls the heat produced in combustion chamber, so that the
engine parts are not damaged & the oil does not leak down.

2. Engine Cooling & Car Radiator
• Heat dissipation is probably one of the most important
considerations in engine design.
• An internal combustion engine creates enough heat to
destroy itself.
• Without an efficient cooling system, we would not have
the vehicles we do today.
• The original radiators were simple networks of round
copper or brass tubes that had water flowing through
them by convection.

3. Engine Cylinder Cooling Systems
• There are mainly two types of cooling systems :
• (a) Air cooled system, and
• (b) Water cooled system.

4. Air Cooled System
• Air cooled system is generally used in small engines say up to
15-20 kW and in aero plane engines.
• In this system fins or extended surfaces are provided on the
cylinder walls, cylinder head, etc.
• Heat generated due to combustion in the engine cylinder will
be conducted to the fins and when the air flows over the fins,
heat will be dissipated to air.
• The amount of heat dissipated to air depends upon :
• (a) Amount of air flowing through the fins.
• (b) Fin surface area.
• (c) Thermal conductivity of metal used for fins

5. Finned Engine Cylinder

6. Cooling System
LIQUID COOLED
•A liquid (coolant) is circulated around the cylinders and
absorb heat from the cylinder walls and cylinder head.
COOLANT is a mixture of antifreeze (Ethylene Glycol) and
Water (some Aluminum radiators have special antifreeze)
•Coolant absorbs heat as it passes through the engine and also
lubricates the water pump.
•Hot coolant enters the radiator in
which the heat is passed on to air that is flowing
through the radiator.
•Prevents rust and corrosion from the water jackets.
•Cooling system level is recommended every two years
in order to remove any rust or contaminants.

7. Liquid cycle In the system

8. Cooling System
Water Jackets
•Designed to keep engine block and cylinder head
cool.
•Open spaces between the outside of cylinder and
inside of cylinder block and head.
•When engine is running at normal operating
temperature, the coolant is forced through the
water jackets in the engine block, through the
head gasket, into the head, and back to the
radiator.
Cylinder head gasket sits between the short block and cylinder head.
•If damaged, the coolant enters the combustion chamber and
the combustion into the cooling system. It will allow acids to form.
(WHITE SMOKE)

9. Cooling System
Water Pump
•Draws the coolant from the radiator,
through the lower radiator hose, and
then forces it through the water jackets,
back into the radiator.
•Water pumps gasket is placed between
the water pump and the engine block to
prevent leakage.
•If the clutch fan can be twisted up and
down, most likely the water pump needs
to be replaced.

10. Cooling System
•Water pump is driven by the crankshaft through
•Timing Belt (Keeps Cam and Crank shafts in time)
•Drive/accessory Belt
V-Belt

11. Cooling System
Engine Fan draws air through the radiator at low speeds.
Fan is mounted on the water pump and
is driven by the drive belt.
•It slips at higher speed, in turn slowing the fan
speed down.
•Should be able to turn when the engine is turned off.
•It locks up at slow speeds, in turn speeding
up the fan RPMs.

12. Cooling System
Radiator is a heat exchanger that removes heat from the coolant passing
through it.
•Vertical or Horizontal core
•Vehicles equipped with automatic transmission
have transmission cooler build into the radiator.
•Some vehicles (towing purposes) have oil cooler
mounted to “or” build into the radiator.

13. Liquid Cooling System

14. Liquids for Engine Cooling

15. Engine Warmup
• As a cold engine heats up to steady-state temperature, thermal
expansion occurs in all components.
• The magnitude of this expansion will be different for each
component, depending on its temperature and material.
• Engine bore limits the expansion of pistons.
• In cold weather, the startup time can be as high as 20—30
minutes.
• Some parts of the engine reach steady state much sooner and
some do not.
• Fairly, normal conditions may be experienced within few
minutes, but it can take as long as an hour to reach optimum
fuel consumption rates.
• Engines are built to operate best at steady-state conditions.
• Full power and optimum fuel economy may not be realized
until this condition is reached.

16. Cold Startup of a SI engine.

17. Thermostat
• The thermostat's main job is to allow the
engine to heat up quickly, and then to
keep the engine at a constant temperature.
• It does this by regulating the amount of
water that goes through the radiator.
• At low temperatures, the outlet to the
radiator is completely blocked -- all of the
coolantis recirculated back through the
engine.
•Once the temperature of the coolant rises to between 82 - 910C, the
thermostat starts to open, allowing fluid to flow through the radiator.
•By the time the coolant reaches 93 - 1030C), the thermostat is open all
the way.

18. Open & Closed Cooling Circuits

19. Cooling System
Hoses
Top Radiator hose brings the coolant back to the radiator and are molded
Specifically for individual make and model.
Lower radiator hose draws the coolant into the
engine, from the radiator and is attached to the
water pump. (sometimes a spring is inserted in
order to prevent collapsing)

20. S I Engine Temperatures
• Three of the hottest points are
around the spark plug, the exhaust valve
and port, and the face of the piston.
• Highest gas temperatures during
combustion occur around the spark
plug.
• This creates a critical heat transfer
problem area.
• The exhaust valve and port operate hot
because they are located in pseudo-
steady flow of hot exhaust gases.
• The piston face is difficult to cool
because its is separated form the water
jacket or finned surface.

21. Cooling of Piston