CHAPTER 39_cooling7.PPT

© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only
Publisher
The Goodheart-Willcox Co., Inc.
Tinley Park, Illinois
by
Russell Krick

 Cooling system functions
 Cooling system operation
 Cooling system types
 Basic cooling system
 Closed and open cooling systems
 Cooling system instrumentation
 Antifreeze
 Block heater

Remove Engine Heat
 Combustion can reach 4500ºF (2500ºC)
 This is hot enough to melt metal parts
 The cooling system removes excess heat

Maintain Operating
Temperature
 180ºF to 210ºF (80ºC to 100ºC)
 Ensures that clearances are correct
when an engine warms to operating
temperature, parts expand
 Ensures proper combustion, minimum
emissions, and maximum performance

Reach Operating
Temperature Quickly
 This minimizes several conditions:
poor combustion (poor fuel vaporization)
part wear
oil contamination
reduced fuel economy
increased emissions

Heater Operation
 The cooling system circulates coolant to
the vehicle’s heater
 Engine heat is used to warm the
passenger compartment

Cooling System

 The water pump forces coolant through
the engine water jackets
 The pump is belt or gear driven off the
crankshaft

Cold Engine Operation
 The thermostat is closed
 The coolant circulates inside the engine
 The engine warms quickly

Hot Engine Operation
 At operating temperature, the
thermostat opens
 Heated coolant then flows through the
radiator
 Excess heat is transferred from the
coolant to the air flowing through the
radiator

 Two common types:
air cooling
liquid cooling

Air Cooling Systems
 Large cylinder cooling fins and outside
air remove excess heat
 The cooling fins increase the surface
area of the metal around the cylinder
 This allows enough heat to transfer to
the outside air
 Plastic or metal shrouds direct air over
the cylinder fins

Liquid Cooling
Systems
 Circulate coolant through the water
jackets
 Combustion heat is transferred to the
coolant
 The cooling system carries it out of the
engine

Liquid Cooling
Advantages
 Precise temperature control
 Less temperature variation
 Reduced emissions
 Improved heater operation

Air Cooling versus
Liquid Cooling

Liquid Cooling
Heat is transferred to cylinder wall and then
into the coolant, where it is carried away

Conventional Coolant
Flow
 Hot coolant flows from the cylinder head
to the radiator
 After being cooled in the radiator, the
coolant flows back into the engine block

Reverse Flow Cooling
 Cool coolant enters the head and hot
coolant exits the block to return to the
radiator
 Helps keep a more uniform temperature
throughout the engine
 Found on high-performance engines

 Components:
water pump
radiator hoses
radiator
fan
thermostat

Water Pump
A ribbed belt powers this pump
Crank
pulley
Water
pump
pulley
Impeller
Ribbed
belt

Impeller Pump
Coolant is thrown outward by centrifugal
force, producing suction in the center of
the pump housing

Water Pump Cutaway
Seal leakage will drip from the vent hole

Coolant Flow

Coolant Flow
(Conventional)
 Coolant flows out of the radiator,
through the lower hose, into the pump
 It then flows through the pump, around
the cylinders, through the heads, up
through the thermostat, and back into
the radiator

Hoses
 Radiator hoses
carry coolant between the engine water
jackets and the radiator
the lower hose is exposed to water pump
suction, so a spring may needed to prevent
collapse
 Heater hoses
carry hot coolant to the heater core
smaller diameter than radiator hoses

Radiator and Heater
Hoses

Radiator Hoses
Two basic types of radiator hoses

Hose Clamps
Three basic types of hose clamps

Radiator
Transfers coolant heat to the outside air

Radiator Types
Downflow Crossflow

Transmission Oil
Cooler
 Often placed in the radiator on cars with
automatic transmissions
 Prevents the transmission fluid from
overheating

Transmission Oil
Cooler
Small tank inside
one of the
radiator tanks

Oil Cooler System

Radiator and A/C
Condenser
 The condenser is usually mounted in
front of the radiator
in this arrangement, heat from the
condenser flows through the radiator,
reducing efficiency
 Side-by-side mounting is sometimes
used

Radiator and A/C
Condenser
This vehicle has
side-by-side
mounting

Radiator Cap
 Seals the radiator
 Pressurizes the system
 Relieves excess pressure
 Allows coolant flow between the radiator
and the coolant reservoir

Radiator Cap

Radiator Cap Pressure
Valve
 Spring-loaded disk
 Normally, water boils at 212ºF (100ºC)
 For each pound of pressure increase,
the boiling point goes up about 3ºF
(1.7ºC)
 Typical pressure:
12–16 psi (83–110 kPa)
raises the boiling point to
250–260ºF (121–127ºC)

Radiator Cap
Vacuum Valve
Opens to allow flow back into the radiator
when the coolant temperature drops

 Closed cooling system
uses an expansion tank
overflow tube is routed into reservoir tank
 Open cooling system
allows excess coolant to leak onto the
ground

Pressure Cap
Operation
Hot engine

Pressure Cap
Operation
Cold engine

Cooling System Fans
 Pull air through the core of the radiator
 Increase the volume of air flowing
through the radiator
 Driven by fan belt or electric motor

Flex Fan
High engine speed causes the blades to
flex, reducing the blowing action

Fluid Coupling Fan
Clutch
Filled with
silicone-based oil
The clutch slips at
higher rpm

Thermostatic Fan
Clutch
 Bimetal spring controls clutching action
cold—clutch slips
hot—clutch locks

Electric Cooling Fans
 An electric motor and a thermostatic
switch provide cooling
 Common on transverse-mounted
engines
 Save energy and increase cooling
efficiency
 Fans only function when needed

Electric Fan Operation
Cold engine

Electric Fan Operation
Hot engine

PCM-Controlled Fans
 When cold, the ECM does not energize
the fan relays
 After warm-up, the ECM feeds current
to the fan relay coils, closing the relay
contacts
 High current flows to fans

PCM-
Controlled
Fans

Radiator Shroud
Ensures that the fan
pulls air through
the radiator core

Thermostat
 Senses the coolant temperature and
controls coolant flow through the
radiator
 Reduces coolant flow in a cold
engine
 Increases coolant flow in a hot
engine

Thermostat
A temperature-sensitive valve

Thermostat Operation
 Cold engine
wax-filled pellet has contracted
spring holds valve closed
 Hot engine
when heated, pellet expands
spring tension is overcome
valve opens

A. Cold engine
B. Hot engine

Cold engine

Hot engine

Bypass Valve
Permits coolant
circulation through the
engine when the
thermostat
is closed

Bypass Thermostat
Blocks off the bypass at operating
temperature
Impeller
Water pump
drive pulley
Water pump
housing
Thermostat
Main flow
Flow to
radiator
Bypass
spring
Bypass
flow
Main
spring

 Two common types:
temperature warning light
engine temperature gauge

Temperature Warning
Light
 When the coolant becomes too hot, a
temperature sending unit (switch) in the
block closes, completing a light circuit
 The warning light glows

Warning Light Circuit

Engine Temperature
Gauge
 Shows the exact operating temperature
 Components:
gauge
variable resistance sending unit

Engine Temperature
Gauge Operation
 When cold, the sending unit has a high
resistance
 Current flow through the gauge is low
 The gauge reads cold
 When hot, the sending unit resistance
lowers
 Current flow through the gauge
increases, the needle deflects to the
right

 Composed of ethylene glycol mixed with
water
 Prevents winter freeze-up
 Prevents rust and corrosion
 Lubricates the water pump
 Cools the engine

Corrosion Protection
Protected with
antifreeze
Water only

Antifreeze/Water
Mixture
Lowers the coolant freezing point
to about –34 ºF (–37 ºC)
50%ANTIFREEZE
50%WATER

 Aids engine starting in cold weather
 120-volt heating element mounted in the
block water jacket
 Common on diesel engines

Block Heater
Installation

Engine and Cooling
System

CHAPTER 39_cooling7.PPT

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CHAPTER 39_cooling7.PPT