Modern Automotive

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PowerPoint for
Modern Automotive Technology
by Russell Krick
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Chapter 39
Cooling System Fundamentals
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Contents

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

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Cooling System Functions
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Remove Engine Heat

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

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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

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Reach Operating Temperature Quickly

• This minimizes several conditions
• poor combustion (poor fuel vaporization)
• part wear
• oil contamination
• reduced fuel economy
• increased emissions

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Heater Operation

• The cooling system circulates coolant to the
  vehicles heater
• Engine heat is used to warm the passenger
  compartment

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Cooling System
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Cooling System Operation

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

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Cold Engine Operation

• The thermostat is closed
• The coolant circulates inside the engine
• The engine warms quickly

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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

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Cooling System Types

• Two common types
• air cooling
• liquid cooling

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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

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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

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Liquid Cooling Advantages

• Precise temperature control
• Less temperature variation
• Reduced emissions
• Improved heater operation

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Air Cooling versus Liquid Cooling
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Liquid Cooling

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

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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

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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

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Basic Cooling System

• Components
• water pump
• radiator hoses
• radiator
• fan
• thermostat

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Water Pump

• A ribbed belt powers this pump

Crankpulley
Impeller
Ribbedbelt
Water pump pulley
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Impeller Pump

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

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Water Pump Cutaway

• Seal leakage will drip from the vent hole

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Coolant Flow
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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

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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

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Radiator and Heater Hoses
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Radiator Hoses

• Two basic types of radiator hoses

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Hose Clamps

• Three basic types of hose clamps

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Radiator

• Transfers coolant heat to the outside air

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Radiator Types
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Transmission Oil Cooler

• Often placed in the radiator on cars with
  automatic transmissions
• Prevents the transmission fluid from overheating

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Transmission Oil Cooler

• Small tank inside one of theradiator tanks

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Oil Cooler System
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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

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Radiator and A/C Condenser

• This vehicle has side-by-side mounting

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Radiator Cap

• Seals the radiator
• Pressurizes the system
• Relieves excess pressure
• Allows coolant flow between the radiator and the
  coolant reservoir

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Radiator Cap
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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
• 1216 psi (83110 kPa)
• raises the boiling point to 250260ºF (121127ºC)

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Radiator CapVacuum Valve

• Opens to allow flow back into the radiator when
  the coolant temperature drops

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Closed and Open Cooling Systems

• 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

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Pressure Cap Operation

• Hot engine

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Pressure Cap Operation

• Cold engine

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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

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Flex Fan

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

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Fluid Coupling Fan Clutch

• Filled withsilicone-based oil
• The clutch slips at higher rpm

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Thermostatic Fan Clutch

• Bimetal spring controls clutching action
• coldclutch slips
• hotclutch locks

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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

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Electric Fan Operation

• Cold engine

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Electric Fan Operation

• Hot engine

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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

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PCM-Controlled Fans
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Radiator Shroud

• Ensures that the fan pulls air through the
  radiator core

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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

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Thermostat

• A temperature-sensitive valve

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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

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Thermostat Operation

• A. Cold engine
• B. Hot engine

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Thermostat Operation

• Cold engine

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Thermostat Operation

• Hot engine

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Bypass Valve

• Permits coolant circulation through the engine
  when the thermostatis closed

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Bypass Thermostat

• Blocks off the bypass at operating temperature

Impeller
Flow toradiator
Water pumpdrive pulley
Bypass spring
Water pumphousing
Bypassflow
Thermostat
Mainspring
Main flow
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Cooling System Instrumentation

• Two common types
• temperature warning light
• engine temperature gauge

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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

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Warning Light Circuit
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Engine Temperature Gauge

• Shows the exact operating temperature
• Components
• gauge
• variable resistance sending unit

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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

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Antifreeze

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

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Corrosion Protection
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Antifreeze/Water Mixture

• Lowers the coolant freezing point to about 34
  ºF (37 ºC)

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Block Heater

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

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Block Heater Installation
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Engine and Cooling System
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Engine and Cooling System