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
© Goodheart-Willcox Co., Inc.
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!
© Goodheart-Willcox Co., Inc.
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
© Goodheart-Willcox Co., Inc.
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