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

Cooling System Functions

Helps Engine Reach Operating Temperature QuicklyHelps Engine Reach Operating Temperature Quickly Maintains Constant Engine Operating TemperatureMaintains Constant Engine Operating Temperature Removes Excess Engine HeatRemoves Excess Engine Heat Provides Heat For Warming the Passenger AreaProvides Heat For Warming the Passenger Area

Helps Engine Reach Operating Helps Engine Reach Operating Temperature QuicklyTemperature Quickly

Advantages of Rapid Engine Warm-upRapid Engine Warm-up:Improved combustion Improved combustion

(better fuel vaporization)(better fuel vaporization)Reduced part wearReduced part wearLess oil contaminationLess oil contaminationIncreased fuel economyIncreased fuel economyReduced emissionsReduced emissions

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Advantages of Maintaining aAdvantages of Maintaining aProper Operating TemperatureProper Operating Temperature

Ensures Proper Combustion Ensures Proper Combustion Minimum Emissions Minimum Emissions Maximum PerformanceMaximum PerformanceMaintains Optimum Fuel EconomyMaintains Optimum Fuel Economy

Maintains Constant Maintains Constant Operating TemperatureOperating Temperature

Thermostat opens and closes to Maintain TempThermostat opens and closes to Maintain Temp 160 ºF to 195 ºF160 ºF to 195 ºF (Depending on thermostat)

When an engine warms to operating temperature parts expand and rapid warm-up reduces part wear

Ensures that clearances are correct

Removes Excess Engine HeatRemoves Excess Engine Heat

On Modern Vehicles, Typical Combustion On Modern Vehicles, Typical Combustion Temperatures can reach 4500 ºF (2500 ºC)Temperatures can reach 4500 ºF (2500 ºC)

This is hot enough to melt metal partsThis is hot enough to melt metal parts Cooling system removes excess heat which can Cooling system removes excess heat which can

cause major engine damage!cause major engine damage!

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Air-cooled EngineAir-cooled Engine

This air-cooled engine has had the cooling fancooling fan and shroudingshrouding removed for better viewing.

The shrouding directs the air-flow around the cylinders

Two common types: air cooling liquid cooling

Cooling Fan & Shrouding Cooling Fan & Shrouding Removed for better viewRemoved for better view

Air Cooling Versus Liquid Cooling

Air Cooling Systems

Large cylinder cooling fins and outside air remove excess heat Cooling fins increase the surface area of the metal around the

cylinder This allows enough heat transfer to the outside air Plastic or metal shrouds duct air onto and around the cylinder finsPlastic or metal shrouds duct air onto and around the cylinder fins

Liquid Cooling Systems

Circulate coolant through the water jackets Combustion heat is transferred to the coolant Cooling system carries it out of the engine Hot coolant flows into the radiator where heat is removed Cooled coolant flows back into engine to repeat this process

Liquid Cooling AdvantagesLiquid Cooling Advantages Precise temperature controlPrecise temperature control Less temperature variationLess temperature variation Reduced emissionsReduced emissions Improved heater operationImproved heater operation

Liquid CoolingHeat is transferred to cylinder wall, into

coolant and 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 Helps keep a more uniform temperature

throughout the enginethroughout the engine Found on high-performance engines

Components:Radiator Radiator HosesFanThermostatWater Pump

RadiatorTransfers coolant heat to the outside airTransfers coolant heat to the outside air

Radiator Types

Vertical FlowVertical Flow Cross FlowCross Flow

Radiator Hoses and Radiator Hoses and Heater HosesHeater Hoses

Hoses Radiator Hoses

Carry coolant between the engine water Carry coolant between the engine water jackets and the radiatorjackets and the radiator

Lower hose is exposed to water pump suction so a spring may prevent collapse

Heater HosesCarry hot coolant to the heater coreSmaller diameter than radiator hoses

Hose ClampsThree basic types of hose clamps

Radiator HosesTwo basic types of radiator hoses

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Radiator FanRadiator Fan

Draws air through the radiator and cools off the hot coolant passing through it.

Thermostat Maintains a constant engine temperatureMaintains a constant engine temperature Helps engine reach operating temperature Helps engine reach operating temperature

quicklyquickly Senses coolant temperature and controls

coolant flow through the radiator Reduces coolant flow on cold engine Increases coolant flow on hot engine

ThermostatA temperature-sensitive valve

Thermostat Operation Cold engine

wax-filled pellet has contractedspring holds valve closed

Hot enginewhen heated, pellet expandsspring tension is overcomevalve opens

Thermostat Operation

A. Cold engine

B. Hot engine

Thermostat OperationCold engineCold engine Hot engineHot engine

Water PumpA ribbed belt powers this pump which pumps coolant throughout the enginepumps coolant throughout the engine.

Crankpulley

Water pump pulley

Impeller

Ribbedbelt

Impeller PumpCoolant is thrown outward by centrifugal force,

producing suction in the center of the pump housing. Straight impeller blades use less energy to operate.Straight impeller blades use less energy to operate.

Water Pump CutawayWater Pump PartsWater Pump Parts

Radiator Types

Vertical FlowVertical FlowTanks on top Tanks on top and bottomand bottom

Cross FlowCross FlowTanks on both sidesTanks on both sides

Transmission Oil Cooler

Often placed in the radiator on cars with automatic transmissions

Prevents transmission fluid from Prevents transmission fluid from overheatingoverheating

Transmission Oil Cooler

Small tank inside one of the

radiator tanks

Water Pump Parts Water pump housingWater pump housing -Iron or aluminum casting that

forms the main body of the pump. Water pump impellerWater pump impeller -Disk with fan-like blades, the

impeller spins and produces pressure and flow. Water pump shaftWater pump shaft -Steel shaft that transmits the

turning force from the hub to the impeller. Water pump sealWater pump seal -Prevents coolant leakage between

pump shaft and pump housing. Water pump bearingWater pump bearing -Plain or ball-bearings that allow the

pump shaft to spin freely in housing. Water pump gasketWater pump gasket -Fits between the water pump and

the engine to prevent leakage. Water pump hubWater pump hub -Provides a mounting place for the

belt, pulley, and fan.

Radiator Hoses and Clamps Radiator hosesRadiator hoses –Carry coolant between the engine water

jackets and the radiator. Flexible hoseFlexible hose –Has an accordion shape and can be bent to

different angles. Molded hoseMolded hose –Manufactured in a special shape, with bends

to clear the cooling fan and other parts. Heater hosesHeater hoses –Small-diameter hoses that carry coolant to

the heater core. Hose springHose spring –Frequently used in the lower radiator hose to

prevent the hose from collapsing. Worm-drive hose clampsWorm-drive hose clamps –Uses a worm gear that engages

slots in the clamp strap to allow tightening around the hose. Hose clampsHose clamps –Hold the radiator hoses and heater hoses

onto their fittings

Radiator Cap Seals the radiatorSeals the radiator Pressurizes the systemPressurizes the system Relieves excess pressureRelieves excess pressure Allows coolant flow between the Allows coolant flow between the

radiator and the coolant reservoirradiator and the coolant reservoir

Radiator Cap

Radiator CapVacuum Valve

Opens to allow flow back into the radiator when the coolant Opens to allow flow back into the radiator when the coolant temperature drops.temperature drops. Without this valve the coolant would Without this valve the coolant would

not flow back into the radiator and the radiator would not flow back into the radiator and the radiator would become low on coolant and the engine would overheat.become low on coolant and the engine would overheat.

Radiator Cap Pressure Valve

Spring-loaded disk Normally, water boils at 212 ºF (100 ºC) For each pound of pressure increase,

boiling point goes up about 3 ºF (1.6 ºC) Typical pressure:

12–16 psiraises boiling point to

250–260 ºF (121–127 ºC)

Closed cooling systemUses an Expansion TankExpansion TankOverflowOverflow tube is routed into reservoir tank

Open cooling systemAllows excess coolant to leak onto the groundground

Pressure Cap Operation

Hot engineHot engine

Cold engineCold engine

Cooling System Fans Pull air through the core of the radiator Increase volume of air through the

radiator Driven by fan belt or electric motor

Flex FanHigh rpm cause blades to flex, High rpm cause blades to flex,

reducing blowing actionreducing blowing action

Fluid Coupling Fan Clutch

Filled withFilled withsilicone-based oilsilicone-based oil

Slips at higher rpmSlips at higher rpm

Thermostatic Fan Clutch

Bimetal spring controls clutching actionBimetal spring controls clutching actionCold—clutch slipsHot—clutch locks

Electric Cooling Fans

Provide cooling with an electric motor and a thermostatic switchProvide cooling with an electric motor and a thermostatic switch Use Use A small direct current motor to operate the cooling fanA small direct current motor to operate the cooling fan Common on transverse-mounted engines Save energy and increase cooling efficiency Fans only function when needed

Electric Fan OperationCold engineCold engine

Hot engineHot engine

PCM-Controlled Fans

When cold, ECMECM does not energize fan relays After warm-up, ECM feeds current to the fan

relay coils, closing relay contacts High current flows to fans

Radiator Shroud

Ensures that the fan Ensures that the fan pulls air through pulls air through the radiator corethe radiator core

Modern Cooling SystemsUse thermostats that are 195°F and higher

(which is higher than older vehicles, 160°F-180°F)

AdvantagesAdvantagesEngines that run higher coolant temperatures: run smoother with more powerrun smoother with more power run more efficiently and use less fuelrun more efficiently and use less fuel burn much cleaner burn much cleaner heaters/defrosters work betterheaters/defrosters work better

Thermostat OperationCold engineCold engine – Thermostat is closed no Thermostat is closed no

coolant flows through the radiatorcoolant flows through the radiator

Bypass Valve

Permits some circulation Permits some circulation through the engine when through the engine when the thermostat is closedthe thermostat is closed

Bypass ThermostatBlocks off the bypass at operating

temperatureImpeller

Water pumpdrive pulley

Water pumphousing

Thermostat

Main flow

Flow toradiator

Bypass spring

Bypassflow

Mainspring

Thermostat Thermostat Jiggle ValveJiggle Valve

The valve allows trapped air to escape when the cooling system is flushed or opened for repairs. The trapped air is a serious problem which could prevent the thermostat from opening and create hot spots with erratic sensor behavior. The air is hard to remove without the valve. Since air rises up in water, the valve should be installed in the 12 o'clock position.

Temperature Warning LightTemperature Warning Light When coolant becomes too hot, a When coolant becomes too hot, a

temperature sending unit (switch) in the temperature sending unit (switch) in the block closes, completing a circuit block closes, completing a circuit and the warning light comes on, letting the and the warning light comes on, letting the driver know there is a problem.driver know there is a problem.

Warning Light Circuit

Composed of ethylene glycol mixed with water Prevents winter freeze-upPrevents winter freeze-up Prevents rust and corrosionPrevents rust and corrosion Lubricates the water pumpLubricates the water pump Raises the boiling pointRaises the boiling point Lowers the freezing pointLowers the freezing point

Antifreeze/Water MixtureA 50/50 mixture is most commonly used

Lowers coolant freezing point to -34 ºFLowers coolant freezing point to -34 ºFRaises the boiling point to 265 ºFRaises the boiling point to 265 ºF

50% ANTFREEZE

50% WATER

Corrosion Protection

Protected with antifreeze

Water only

Aids engine starting in cold weather 120-volt heating element mounted in the

block water jacket Common on diesel engines

Block Heater Installation

Questions?Questions? Refer to Duffy textbook chapter 39Refer to Duffy textbook chapter 39 Scroll back through power-pointScroll back through power-point Ask fellow student for helpAsk fellow student for help After following all the above steps,

check with your instructor