Level one cooling systems

1. Motor Vehicle Level I.
Name
Cooling system

2. Engine Cooling Systems
This presentation will explore:
 Cooling Systems
 Cooling System Components
 Fans
 Coolant Characteristics

3. Objectives
By the end of this lesson, you should be able to:
 Describe the scientific principles which govern the operation of cooling
systems
 State the purpose and requirements of a cooling system
 Describe the effects of:
 Overheating of the engine
 Overcooling of the engine
 Identify the component parts of a cooling system
 Describe the function, operation and purpose of cooling system
components.

4. Dissipation of
Heat Energy
20% to power at wheels
5% to engine losses
28% to the cooling system.
45% to exhaust
3% to transmission losses

5. The Effects of Overheating
 Distortion due to uneven expansion
 Burnt, or carbonised lubricant
 Reduction in volumetric efficiency
 Pre-ignition.

6. The Effects of Overcooling
 Incomplete vaporisation of fuel
 Condensation of water vapour.

7. Heat is transferred in 3 ways:
 Conduction
 Convection
 Radiation.
Thermo-siphon Cooling System

8. Air cooling requires a large volume of air
flow around the engine.
Air
The cylinder has cooling fins to improve
radiation of heat. The large surface area
of the fins, transfers heat to the
surrounding air.
Fins are usually longer at the rear
because the air is pushing from the front
so it aids the cooling process.
Rubber tubes are fitted inside the fins on
the cylinder head to stop high frequency
vibrations.
Air
cooling

9. A manual heater flap is used to control
the heating in the passenger
compartment. This is to allow hot air to
flow through ducting into the vehicle.
Air
Centrifugal fans are used- air is blown
through a radiator which cools the air
before it enters the engine
compartment. Cool air is sent through
cowling and ducting into the engine
compartment
Heated air radiates into the atmosphere.
Air
cooling

10. Water
Water cooling provides better control and
stability of the engine temperature.
With water cooling, the coolant
circulates around a water jacket to
absorb the heat energy.
The coolant is a mixture of water and
antifreeze and anticorrosion additives.
Water cooling

11. Combustion temperatures in the cylinders can reach 2500ºC (4500ºF). If
uncontrolled, these high temperatures can cause damage to the engine.
Cooling System
Coolant absorbs heat energy in the cylinder by conduction, radiating the
excess heat to the air by use of the radiator.
Normal coolant operating temperatures are about 80-100ºC (180-210ºF).
The rate of air flow over the radiator may be increased by the use of a fan.

12. Gas enters the cylinder at
about 400 C
Overview
Combustion raises the
temperature to around
20000 C
By the end of the
power stroke, gas is
around 12000 C
Exhaust gas leaves
the cylinder at about
8000 C.
1,2000C
2,0000C
400C 8000C

13. Purpose of the water pump
 Allows smaller quantity of coolant to be used
 Directs coolant to where it is most needed
 Allows cross-flow radiator to be used
 Allows lower radiator and bonnet.

14. The Water Pump
Delivery outlet
Casing
Impeller
Gland seal
Oil seal
Drive flange
Bearings
Leakage outlet
Intake

15. Water Pump Location

16. Water Pump
The water pump forces coolant
through the engine cylinder block
and head channels.
Coolant is drawn into the centre of
the water pump via the lower hose
of the radiator.
If a mechanical cooling fan is
used, it may often be attached to
the water pump hub.
Centrifugal force, due to the rotation
of the water pump impeller, throws
the liquid out at the edge and into
the cylinder block.
Leak bore
Drive
pulley
Impeller
Water
pump
housing
Bearings
Main
shaft
Seal

17. Water Flow
Conventional coolant flow is
upward past the cylinders (hot
liquid rises).
Coolant then flows out from
the cylinder head to the
radiator via its top hose. The
hot coolant is then cooled as
it travels through the radiator.
The water pump draws
coolant from the bottom of the
radiator and forces it back
through the cylinder block.
Reverse flow cooling is unusual,
but is in the opposite direction
from that described above.
Pipes to passenger
compartment heater
Water cooled
inlet system
To top
hose
Thermostat
housing
From bottom
hose
Coolant flow
around cylinders

18. Radiator
Hoses connect the radiator to
the engine cylinder block
(water jacket) and passenger
compartment heater.
A thermostat controls the
coolant flow during warm-up,
so that the engine reaches
operating temperature quickly.
The function of the radiator is
to transfer unwanted heat
energy from the coolant to the
outside air.
Fan(s) draw air through and
over the radiator to increase
the air flow and improve
cooling efficiency.
Radiator
hoses
Coolant flow within engine
Pump
Fan
Cross flow
radiator

19. Downflow Radiators
Tanks at the top and bottom of the
radiator act as reservoirs for the coolant.
Coolant flows down through the core
tubes, which have cooling fins attached,
allowing heat energy to be dissipated.
The coolant flows out of the bottom tank
back to the engine via the water pump.
In vehicles with automatic transmission, oil
coolers are often placed in the bottom tank
of the radiator, enabling transmission oil to
be cooled.

20. Crossflow Radiators
Crossflow radiators are typically
used in modern vehicles, as they
allow low engine compartments
and lower bonnet line.
The reservoir tanks are found on
each side of a crossflow radiator.
The core tubes carrying the
coolant, run horizontally.
For vehicles with automatic
transmission, the oil cooler is in
the return tank (shown on the right
in the diagram).

22. Hoses
Flexible rubber hoses carry the coolant between the radiator, engine block
and heater core. As they are flexible, they allow for engine vibrations without
damage to the components.
The upper hose
carries water to the
radiator from the
cylinder head.
An expansion tank reservoir is used to keep the system topped up.
The lower hose connects
the radiator back to the
water pump.
Smaller hoses carry hot coolant to the
passenger compartment heater.

23. Types of Hoses
Moulded hoses are typically pre-
formed for a particular make and
model of vehicle.
A support spring is sometimes fitted inside the radiator hose to prevent it
collapsing under low pressure when the engine is cold.
There are a number of different types and materials of radiator hose,
ranging from natural rubber construction to high temperature resistant
silicone types.
The construction of the hose, by use
of materials such as synthetic yarn,
styrene rubber or synthetic materials,
provides a tough yet flexible hose capable of
resisting coolant, abrasion, flexing, ultraviolet and
dilute acids, which may degrade the hose over time.
Moulded hose
Flexible hose

24. Purpose of the pressure cap
 Eliminates coolant loss due to surge
 Prevents lowering of boiling point due to atmospheric pressure
 Allows engine to be run at higher temperature
 Permits use of less coolant

25. The Pressure Cap
Pressure spring
Vacuum valve
Pressure seal
Radiator filler neck
Overflow

26. Pressure Cap Location

27. Radiator Cap
The radiator pressure cap pressurizes the coolant system in order to raise
the coolant’s boiling point to about 125ºC (255ºF), this overcomes the
production of steam.
The pressure valve
opens when the coolant
system temperature rises
significantly, to allow the
escape of excess coolant
to an expansion bottle.
The surplus coolant is released and held in an expansion tank (in a closed
system). Or in older vehicles, spills to the ground (in an open system).

28. Radiator Cap

29. Purpose of expansion tank
 Prevents loss of coolant due to expansion
 Allows the use of less coolant
 Fitted high as a header tank, it allows a cross-flow radiator to be used

30. The expansion tank
Pressure cap
Overflow pipe
Air vent
Expansion tank

31. Location of expansion tank
Pressure cap
Radiator
Filler cap
Overflow pipe
Expansion tank

32. Closed Cooling System
The radiator top tank is connected via the pressure cap to an expansion tank.
When the engine cools,
a vacuum valve in the
pressure cap opens to
allow the coolant to
flow back to the
radiator top tank.
When the engine is hot,
excess coolant flows to
the expansion tank.

33. Engine-Powered Fan
Mechanical fans provide air flow across the
radiator core tubes and may be bolted to the
water pump hub.
A spacer may be needed in order to place
the fan near to the radiator.
Fluid coupling fan clutches are arranged
to slip at higher speeds when natural air
flow is likely to be increased.
The blades of the fan may be flexible or fixed.
Thermostatic fan clutches slip at cold
temperatures, reducing air flow through the
radiator and speed warm-up. When the
coolant reaches the operating temperature, the
clutch locks and the fan rotates in a fixed manner.
Belt pulley

34. Electric Cooling Fan
Electric fans use DC (direct current)
motors coupled to a thermostat switch.
The fan is operated to prevent overheating
when the coolant’s temperature increases
beyond its optimum value.
At low temperature:
At high temperature:
 Low temperature is indicated on
the gauge,
 The thermostat switch is open so
there is no current feeding the motor.
 High temperature indication on
the gauge,
 Thermostat switch is closed,
 Current feeds the fan motor.
Temperature
sending unit
Thermostat
switch

35. Antifreeze
At sea level the temperature range for water to
remain as a liquid is from 0º-100ºC (32º-212ºF).
Other advantages of antifreeze are:
With the engine coolant system pressurized,
the boiling point is raised to about 125ºC (255ºF).
The main disadvantages of using water in
the coolant system is that it can freeze in
winter conditions, and cause corrosion.
Therefore, to prevent this, antifreeze
(Ethylene Glycol) is added to the water in
order to lower its freezing point to about
-37ºC (-34ºF), in the case of a 50% mix.
 Prevents winter freezing
 Resists rust and corrosion
 Lubricates the water pump
Boiling
Freezing

36. Summary
Can you now describe how the following scientific
principles are used within the system:
 Conduction
 Convection
 Radiation?

37. Summary
 Can you now describe the following:
 Purpose and requirements of a cooling system
 Effects of:
 Overheating of the engine
 Overcooling of the engine
 Function, operation and purpose of cooling
system components?