The engine cooling system works to maintain an efficient operating temperature for the engine. It uses either air or liquid cooling methods. Liquid cooling uses a pressurized closed system to circulate a coolant mixture of water and antifreeze through water jackets in the engine and back to a radiator, where a fan helps dissipate heat to the air. Key components include the water pump, radiator, thermostat, hoses, and pressure cap. The cooling system works to absorb up to 35% of the engine's heat and reject it to keep components within their optimal temperature range.

1. ENGINE COOLING SYSTEM

2. Purpose
 Keep engine at its most efficient
temperature
 In combustion process the temperature
of gases is 2200°c
 Coming to walls of cylinder it is 180 -
260°c
 This temperature should maintain
 More heat should not absorb by cooling.
up to 35% of heat

3. Types of Cooling
 Air cooling
 Liquid cooling

4. Air cooled Engine
 Metal fine are extended to cylinder walls
 Engine exposed to air
 Shrouds and fans are used in some
engines
 Engines are open not grouped

5. Water Cooled Engines
 Coolant circulate around cylinder walls
 It takes the heat by convection process
 Coefficient of heat transfer is higher in
liquids
 Coolant is a mixture of water and
antifreeze. (Normally 40/60 mixture)

6. How it Works:
Liquid Cooled Systems - A pressurized closed circulation system

7. Parts of a Liquid Cooling System
 Radiator & Pressure
Cap
 Fan & Belt
 Coolant Pump
 Water Jackets
 Thermostat
 Hoses
 Coolant

8. Water jackets
 Open space between outside and inside
walls of cylinder
 The coolant circulates freely around
engine hot spots
 It includes valve seats and guides and
upper parts of cylinder where piston and
rings slides

9. Water jackets

10. Water pump
 Impeller type centrifugal pumps
 Placed at front end of cylinder block and
back to radiator
 It can circulate 28,390 lit of coolant per
hour
 It consist inlet, outlet, impeller, bearings
and seals

11. Water Pump

12. Engine Fan
 To pull air through radiator
 It improves cooling at slow speeds
 Four to six blades, shrouds
 Variable speed fan
 Flexible blade fan
 Electric fans

14. Radiator
 Heat exchanger device
 It holds large volume coolant in close
contact with large amount of air
 Cores and pipes
 Inlet tank and sink
 Down flow and cross flow

16. Expansion tanks
 Separate plastic reservoir
 Recovery tank
 Connected to over flow
 Coolant in engine is expands…contrasts
 Surge tank
 An advantage to the use of an expansion
tank is that it eliminates almost all air
bubbles from the cooling system. Coolant
without bubbles absorbs heat better.

18. Transmission oil coolers

19. Thermostat
 Thermostatic device
 Wax pellet
 85 to 90°c
 It is placed at passage from cylinder
head to upper tank of radiator

22. Radiator Pressure cap
 Sealing and pressurizing

23. Anti Freeze Solutions
 An antifreeze is a chemical additive which
lowers the freezing point of a water-based
liquid
 Lowers galvanic corrosion
 Maintain small viscosity to water
 methanol (methyl alcohol)
 propylene glycol
 5% additives
 sodium silicate, disodium phosphate, sodium
molybdate, sodium borate, and dextrin
 dye (commonly a green, red, orange, yellow,
or blue fluorescent)

24. Temperature indicator
 Balancing coil gauge
 Bimetallic thermostat gauge
 Indicator light