The automobile cooling system uses coolant, a water pump, radiator, and fan to maintain the engine's temperature. It circulates coolant through passages in the engine and radiator to absorb heat from the engine. The thermostat regulates coolant flow to help the engine reach optimal temperature quickly and maintain temperature under different operating conditions. The radiator, located in the vehicle's airflow, cools the coolant and the pressurized cooling system increases the coolant's boiling point to protect against overheating.

1. Automobile Cooling System

2. The cooling system forms an intrinsic part of an
automobile engine. It performs multitude of
functions such as removing excess heat from
the engine, maintaining efficient temp and
allowing engine to perform its task within a short
span of time. Ideally, automobile cooling system
keeps the engine running at an optimum temp
whatever the operating conditions are.
Introduction
Temps in the combustion chamber of the
engine can reach 4,5000
F (2,5000
C), so cooling
the area around the cylinders is critical.

3. Automobile Cooling System consists of
components or equipment installed in vehs for
removing heat from all the moving parts so that
they can work suitably without 1.melting,
2.seizing and 3. overheating. More specifically,
automotive cooling system makes use of 1.
coolant, 2. lubricating oil and 3. fan to maintain
and regulate the temp of other parts of an
engine.
Automobile Cooling System

4. a. To keep the engine at its most efficient temp
at all speeds and operating conditions.
b. To take away extra heat before it damages
engine parts.
c. It also helps bring the engine up to normal
operating temp as quickly as possible

5. Automobile Cooling System

6. Automobile Cooling System

7. Over Cooling
 It results in losing some of the heat
used for expanding the gases to vaporize
the fuel.
 Gases will condense on cylinder walls.
 Thus lubrication will be affected
causing greater frictional loss.
Question: What are the results of overcooling?

8. Under coolingUnder cooling
Under cooling results in burning away
the lube oil film, boiling and evaporation
of cooling water which will create
additional frictional wear of engine.
boil hobe evaporate hobe , oil film burn hoye jabe , lub oil friction
wear

9. Types of Cooling SystemTypes of Cooling System
Basically, there are two types of automobile
cooling systems, which are widely used by the
automobiles namely:
a. Direct Cooling/Air Cooling system.
b. Indirect Air/ Liquid Cooling system

10. Air Cooling SystemAir Cooling System
The engine block is
covered in aluminum fins
that conduct the heat
away from the cylinder. A
powerful fan forces air
over these fins, which
cools the engine by
transferring the heat to
the air.

11. Air-cooling is mostly used by airplanes,
motorcycles and lawn mowers. Air cooling
system is feasible for only small vehicles and
equipment, as air-cooled engines do not operate
at consistent temp and command extensive use
of aluminum to disperse heat.
Air Cooling SystemAir Cooling System

12. The amount of heat dissipated to the cooling
air depends upon:
 Total surface area of the fins.
 Velocity and amount of the cooling air.
 Temp of the cylinder fins and cooling air.

13.  Cheaper to manufacture.
 No topping up of cooling system is
required.
 Does not freeze up and no anti-freeze is
required.
 Cylinder and cylinder head casting are
less complicated.
 Engine wt is reduced.
 Its bulk is reduced.
 Engine warms up faster.
Advantages of Air Cooling System:

14. Disadvantages of Air Cooling System:
 Difficult to maintain even cooling all around
the cylinder.
 Not suitable for multi cylinder engines.
 Cooling system efficiency is less than water
cooling.
 More noisy.

15. Water Cooling SystemWater Cooling System

16. Water Cooling SystemWater Cooling System

17. Water Cooling SystemWater Cooling System
The fluid circulates through pipes and
passageways in the engine. As the liquid passes
through the hot engine it absorbs heat, cooling
the engine. After the fluid leaves the engine, it
passes through a heat exchanger, or radiator,
which transfers the heat from the fluid to the air
blowing through the exchanger.
The liquid-cooling system for automobiles offers
the most positive cooling and it maintains an
optimum engine temp.

18. Automobile Cooling System

19. The pump sends the fluid into the engine block, where it
makes its way through passages in the engine around
the cylinders. Then it returns through the cylinder head
of the engine. The thermostat is located where the fluid
leaves the engine. The plumbing around the thermostat
sends the fluid back to the pump directly if the
thermostat is closed. If it is open, the fluid goes through
the radiator first and then back to the pump. There is
also a separate circuit for the heating system. This
circuit takes fluid from the cylinder head and passes it
through a heater core and then back to the pump.
Water Cooling SystemWater Cooling System

20. Advantages of Water Cooling
 More suitable for multi cylinder engines.
 Small amount of water is require to
absorb a large amount of heat.
 Engine temp can be control properly
due to use of thermostat.
 Water jackets reduce the engine noise.
 It is easier to install the heating system
in a car.

21. Disadvantages Of Water Cooling
 Water freezes and causes damage.
 Engine may run hot or get seized if there
is any loss of water .
 More expensive than air cooling..
 System is heavy and bulky.

22. The main Components of Water Cooling
System are as follows:
a. Radiator
b. Thermostat
c. Pump
d. Fan
e. Hose
f. Heater (Auxiliary)
Components of Water Cooling System

23. 3. Thermostat.
Main Components of water cooling
system:
a. Water Jackets.
b. Water Pump.
c. Thermostat.
d. Radiator.
(1) Radiator pressure cap.
(2) Expansion Tank / Recovery Tank..
e. Fan.
f. Hose.
g. Heater (Auxiliary).

24. Water Jackets
The water jackets are open
spaces between the
cylinder walls and the
outside shell of the block
and head. Coolant from the
water pump flows first
through the block water
jackets. Then the coolant
flows up through the
cylinder head water jackets
and back to the radiator.

25. Water Pump
The heart of the cooling
system is the water
pump. Its job is to move
the coolant through the
cooling system. The
water pump is driven by
the crankshaft through
pulleys and a drive V
belt.

26. Automobile Cooling System

27. The inlet to the pump is located near the center
so that fluid returning from the radiator hits the
pump vanes. The pump vanes fling the fluid to
the outside of the pump, where it can enter the
engine.
The fluid leaving the pump flows first through the
engine block and cylinder head, then into the
radiator and finally back to the pump.
Water Pump

28. Thermostat
The thermostat is a
heat operated valve
that regulates coolant
temp. When the
engine is cold, the
thermostat closes. As
the engine warms up,
the thermostat opens.
It allows or prevent
coolant flow through
the radiator.

30. The thermostat's main job is to allow the engine
to heat up quickly, and then to keep the engine
at a constant temp. It does this by regulating the
amount of water that goes through the radiator.
At low temps, the outlet to the radiator is
completely blocked - all of the coolant is re-
circulated back through the engine.
Thermostat

31. The thermostat opens at a specific temp or
thermostat rating. Two common ratings are 850
C
and 910
C. Most thermostats begin to open at
their rated temp. They are fully open about 110
C
higher.
Once the temp of the coolant rises to between
(82 - 910
C), the thermostat starts to open,
allowing fluid to flow through the radiator. By the
time the coolant reaches 93 to 1030
C, the
thermostat is open all the way.
Thermostat

32. a. To block the coolant flow to the radiator.
b. To allow the coolant flow to the radiator.
c. To regulate the engine temperature.
Functions:

33. There are several types of automotive
thermostat. A heat sensitive wax pellet operates
most thermostats. It expands with increasing
temp to open the valve.
Types:
a. Bellows or Aneroid type
b. Wax or Hydrostatic type
Thermostat

34. Bellows Type Thermostat

35. Wax Thermostat
Components:
 Copper Loaded Wax
 Rubber Plunger

36. THERMOSTAT

37. Radiator
The radiator is basically a heat
exchanger , transferring heat from
the engine to the air passing
through it by the fan. The radiator
itself is a series of tubes and fins
that expose the coolant's heat to as
much surface area as possible. In
the radiator, coolant loss heat to
the passing air. Radiator has three
main parts as follows:

38. a. Inlet Tanks/ Upper Tank .
b. Radiator Core.
c. Outlet Tanks/Lower Tank
Radiator

39. Radiator

40. Radiator Pressure Cap
Radiator pr caps are
equipped with pr springs and
vents. It has a pr relief valve
and a vacuum relief valve.
Caps are normally designed
to hold the pr between 14 to
17 psi ( 96.53 and 117.21
kPa). For increasing pr one
pound the boiling point raised
about 1.80
C .

41. When the fluid in the cooling system heats up, it expands,
causing the pr to build up. The cap is the only place where
this pr can escape, so the setting of the spring on the cap
determines the maximum pr in the cooling system. When
the pr reaches 15 psi, the pr pushes the valve open,
allowing coolant to escape from the cooling system. This
coolant flows through the overflow tube into the bottom of
the overflow tank. This arrangement keeps air out of the
system. When the radiator cools back down, a vacuum is
created in the cooling system that pulls open another
spring loaded valve, sucking water back in from the bottom
of the overflow tank to replace the water that was expelled.
Radiator Pressure Cap

42. Function of radiator pr cap
♦ The cap allows for increase in pr in the
radiator, which raises the boiling point of the
coolant. The radiator cap actually increases the
boiling point of the coolant by about 450
F (250
C).
♦ Sealing reduces coolant losses from
evaporation.
♦ When the pr goes too high, it raises the pr
relief valve. Excess pr and coolant then escape
into the expansion tank.

43. ♦ It protects the system from developing a
vacuum that could collapse the radiator. When
the engine is shut off and begins to cool, the
coolant contracts and a vacuum develops in the
cooling system. This pulls open the vacuum
valve. Coolant from the expansion tank then
flows back into the cooling system.
Function of radiator pr cap

45. Expansion Tank
Expansion tank is designed/used to catch and hold any
coolant that passes through the pr cap when the engine
is hot. It is partially filled with coolant and connected by
an overflow tube to the radiator.
As the engine warms up, the coolant expands. This
eventually causes the pr cap release. The coolant
passes to an expansion tank.
When the engine is shut down, the coolant begins to
shrink. Eventually , the vacuum spring inside the pr cap
opens and the coolant in the expansion tank is drawn
back into the radiator.

46. Expansion Tank

47. Expansion Tank

48. Engine Fan
The radiator sometimes
needs additional airflow
through it to prevent the
engine from
overheating. An engine
fan pulls the additional
air through the radiator.
The fan may be either a
mechanical fan or an
electric fan.

49. Mechanical Fan
Engines mounted
longitudinally in rear-
drive vehicles usually
have a mechanical fan
that mounts to the
water-pump shat.

50. Electric Fan
Transverse engines in front-drive vehicles
usually have an electric fan. An electric motor
turns the blades. A thermostat switch turns on
the fan only when needed.
Advantage of an Electric Fan
♦ An electric fan drains less power from the
engine.
♦ Creates less noise than a mechanical fan.
♦ There is no fan belt to inspect, adjust or
replace

51. Hoses
Function:
 To carry hot and cold streams of liquid to the
radiator and the engine channel.
 The interconnecting hoses from radiator to
engine and from engine to cabin heater and
back again are very special.
Construction:
 Radiator to engine hoses -metal coil
reinforced hoses.
 The bottom hose.
 Hose clamps.

52. Hoses

53. Heater
Functions:
 Act as a secondary
cooling system
 It is not an electric
heater

54. COOLANT
Coolant is actually a mixture of water and
ethylene glycol-based antifreeze. Water alone
has a boiling point of 1000
C at sea level.
A mixture of 67% antifreeze and 33% water will
raise the boiling point of the mixture to 1130
C
and lower the freezing point to – 690
C.
If the % is lower than 44%, engine parts may be
eroded by cavitations and cooling system
components may be severely damaged by
corrosion.

55. COOLANT
Recommended mixture is a 50/50 solution of
water and antifreeze. The anti freeze
concentration minimum of 44% all year and in
all climates.
If the % is 100%, engine will be extremely
heated

56. Coolant performs three basic jobs:
♦ It lowers the freezing point of the engine
coolant to −370
C.
♦ It raises the boiling point of the engine
coolant to 1080
C.
♦ It helps protect the cooling system metals
from deposits and corrosion.

58. ENGINE OVERHEATING
POSSIBLE CAUSES
Low coolant level
Loose fan belt.
Pressure cap defective.
Radiator obstructed.
Fan drive clutch defective
Inadequate coolant flow
REMEDY
Fill as require.
Adjust.
Replace.
Repair/clean
Replace/Repair.
Check pump.