halderman ch021 lecture

© 2011 Pearson Education, Inc.All Rights Reserved

Automotive Technology, Fourth EditionJames Halderman

COOLING SYSTEM OPERATION AND

DIAGNOSIS

21

21 COOLING SYSTEM OPERATION AND DIAGNOSIS



ObjectivesObjectives• The student should be able to:

– Prepare for ASE Engine Repair (A1) certification test content area “D” (Lubrication and Cooling Systems Diagnosis and Repair).

– Describe how coolant flows through an engine.

– Discuss the operation of the thermostat.




ObjectivesObjectives• The student should be able to:

– Explain the purpose and function of the radiator pressure cap.

– Describe the operation and service of water pumps.

– Discuss how to diagnose cooling system problems.




COOLING SYSTEMCOOLING SYSTEM




Cooling SystemCooling System• Purpose and Function

– Cooling system operation depends on design and operating conditions

– Basis of cooling system design





– Basis of cooling system design• Heat output of engine• Radiator size





– Basis of cooling system design• Type of coolant • Size of water pump (coolant pump)





– Basis of cooling system design• Type of fan, thermostat, system pressure





– Cooling system must allow engine to warm up to operating temperature rapidly and then maintain temperature





– Peak combustion temperature from 4,000°F to 6,000°F (2,200°C to 3,300°C)





– Average combustion temperatures from 1,200°F to 1,700°F (650°C to 925°C)





– Continued operation at these temperatures will weaken engine parts

– Cooling system keeps head and cylinder walls at temperature for maximum efficiency





– Cooling system removes about one-third of heat

– One-third of heat escapes through exhaust system




Figure 21-1 Typical combustion and exhaust temperatures.




Cooling SystemCooling System• Low-Temperature Engine Problems

– Operating temperatures must be above minimum temperature

– Failure to reach specified temperature may cause engine-related faults





– PO128 diagnostic trouble code (DTC)• Code indicates “coolant temperature below

thermostat regulating temperature”





• Usually a defective thermostat staying open or partly open





– Moisture created by combustion process• Can condense and flow into oil





– Moisture created by combustion process• Each gallon of fuel produces moisture equal

to one gallon of water





– Moisture created by combustion process• Condensed moisture combines with

unburned hydrocarbons and additives





– Moisture created by combustion process• Forms carbonic acid, sulfuric acid, nitric

acid, hydrobromic acid, hydrochloric acid




Cooling SystemCooling System• Most manufacturers offer block heaters

– Plug into household current (110 volts AC)– Heating element warms coolant




Cooling SystemCooling System• High-Temperature Engine Problems

– Maximum engine temperature limits required to protect engine

– Higher than normal temperatures can cause engine-related issues





– Oxidation of engine oil producing hard carbon and varnish

• Varnish causes hydraulic valve lifter plungers to stick





– Higher than normal temperatures causes oil to become thinner

• Thinned oil will cause excessive oil consumption





– High coolant temperatures raise combustion temperature and cause detonation (spark knock or ping)




COOLING SYSTEM COOLING SYSTEM OPERATIONOPERATION




Cooling System OperationCooling System Operation• Purpose and Function

– Coolant flows through engine, picks up heat

– Coolant flows to radiator, heat is passed to outside air




Figure 21-2 Coolant circulates through the water jackets in the engine block and cylinder head.




Figure 21-3 Coolant flow through a typical engine cooling system.




Cooling System OperationCooling System Operation• Cooling System Operation

– Coolant temperature rises up to 15°F (8°C) as goes through engine and cools as it goes through radiator





– Coolant flow rate may be 1 gallon (4 liters) per minute for each engine horsepower





– Hot coolant comes out of thermostat housing on top of engine in most engines





– Engine coolant outlet connects to radiator by upper radiator hose and clamps





– Coolant is cooled by air flowing through radiator

– Coolant leaves radiator through outlet and lower radiator hose





– Coolant flows to the inlet on water pump, which recirculates it through engine





– NOTE: Some newer engine designs place thermostat on inlet side of water pump. Thermostat closes until coolant temperature causes it to open. Placement on inlet side reduces rapid temperature changes.




THERMOSTATSTHERMOSTATS




ThermostatsThermostats• Purpose and Function

– Thermostat controls minimum normal temperature

– Thermostat is temperature-controlled valve place at engine coolant outlet on most engines




ThermostatsThermostats• Thermostat Operation

– Encapsulated wax-based plastic pellet heat sensor on engine side of thermostatic valve

– Engine heat swells the heat sensor




Figure 21-4 A cross section of a typical wax-actuated thermostat showing the position of the wax pellet and spring.





– Mechanical link opens thermostat valve– Open thermostat allows some coolant to

flow to radiator





– Remaining coolant flows through bypass to engine

– Rated temperature of thermostat indicates temperature at which thermostat opens




Figure 21-5 (a) When the engine is cold, the coolant flows through the bypass.




Figure 21-5 (b) When the thermostat opens, the coolant can flow to the radiator.





– Thermostat fully open at about 20°F higher than opening temperature




Chart 21-1 The temperature of the coolant depends on the rating of the thermostat.




Figure 21-6 A thermostat stuck in the open position caused the engine to operate too cold. If a thermostat is stuck closed, this can cause the engine to overheat.





– NOTE: Bypass around closed thermostat allows coolant to circulate during engine warm-up. Bypass may be cast or drilled into engine and pump parts.




Figure 21-7 This internal bypass passage in the thermostat housing directs cold coolant to the water pump.




Figure 21-8 A cutaway of a small block Chevrolet V-8 showing the passage from the cylinder head through the front of the intake manifold to the thermostat.




ThermostatsThermostats• Thermostat Testing

– Hot Water Method• Thermostat is removed and suspended in

water using 0.015 in. (0.4mm) feeler gauge with a thermometer





– Hot Water Method• Container is heated until thermostat opens





– Hot Water Method• Opening temperature should be within 5°F

(4°C) of temperature on thermostat





– Infrared Thermometer Method• Infrared thermometer (pyrometer) measures

temperature near thermostat





– Infrared Thermometer Method• As engine warms, temperature reaches

thermostat opening temperature





– Infrared Thermometer Method• As thermostat opens, coolant temperature

drops





– Infrared Thermometer Method• As thermostat cycles, temperature ranges

from opening temperature to 20°F (11°C) above opening temperature





– Infrared Thermometer Method• NOTE: If temperature rises more than 20°F

(11°C) check for restriction, low coolant flow, clogged radiator




ThermostatsThermostats• Scan Tool Method

– Scan tool reads actual temperature detected by ECT sensor




ThermostatsThermostats• Thermostat Replacement

– Overheating engine may result from faulty thermostat

– Engine that does not get warm always indicates faulty thermostat





– To replace thermostat, drain coolant from radiator to below level of thermostat





– Remove hose from thermostat housing neck

– Remove housing to expose thermostat





– Clean gasket flanges and thermostat housing

– Place thermostat in engine with sensing pellet toward engine




Figure 21-10 Some thermostats are an integral part of the housing. This thermostat and radiator hose housing is serviced as an assembly. Some thermostats snap into the engine radiator fill tube underneath the pressure cap.





– Install thermostat housing with new gasket or O-ring

– CAUTION: Failure to set thermostat into recessed groove will cause housing to tilt.





– Tightening bolts will usually crack housing, creating leak




RADIATORSRADIATORS




RadiatorsRadiators• Types

– Serpentine fin core– Plate fin core





– In each type, coolant flows through oval-shaped core tubes

– Heat is transferred to cooling fins





– Air flows through radiator and removes heat

– Older radiators made from yellow brass




Figure 21-11 The tubes and fins of the radiator core.




Figure 21-12 (a) A radiator may be either a down-flow or a crossflow type.




Figure 21-12 (b) A radiator may be either a down-flow or a crossflow type.





– Since 1980s, radiators made from aluminum with nylon-reinforced plastic side tanks





– Core tubes are 0.0045 to 0.012 in. (0.1 to 0.3 mm) sheet brass or aluminum





– Two Basic Designs:• Down-flow radiators• Cross-flow radiators




RadiatorsRadiators• How Radiators Work

– Main limitation of heat transfer is from radiator to the air

– Heat transfers from water to fins up to seven times faster than from fins to air





– Radiator must remove heat equal to heat energy produced by engine

• Each horsepower equals 42 BTUs (10,800 calories) per minute





– Radiator capacity by be increased by increasing core thickness or packing more material in same volume, or both





– NOTE: Lower air dam in front of vehicle directs air through radiator. Damaged or missing air dam can cause engine to overheat.





– When transmission oil cooler is used, it is placed in outlet tank




Figure 21-13 Many vehicles equipped with an automatic transmission use a transmission fluid cooler installed in one of the radiator tanks.




PRESSURE CAPSPRESSURE CAPS




Pressure CapsPressure Caps• Operation

– Cap has spring-loaded valve that closes cooling system vent

– Cooling pressure builds up to pressure setting of cap





– Cap releases excess pressure– Pressure raises boiling temperature of

coolant• Boiling temperature increases about 3°F

(1.6°C) per pound of pressure





– Pressure raises boiling temperature of coolant

• At sea level, water boils at 212°F (100°C)





– Pressure raises boiling temperature of coolant

• 15 PSI (100kPa) pressure cap increases boiling temp to 257°F (125°C)




Pressure CapsPressure Caps• Functions

– Specified coolant system temperature serves two purposes:

• Allows engine to run at efficient temperature, close to 200°F (93°C)






• The higher the coolant temperature, the more heat it can transfer






• For proper cooling, system must have right pressure cap





– Vacuum valve allows coolant to flow back to radiator when it cools down

– NOTE: Proper pressure cap especially important at high altitudes.




Figure 21-14 The pressure valve maintains the system pressure and allows excess pressure to vent. The vacuum valve allows coolant to return to the system from the recovery tank.






• Boiling point of water lowered by about 1°F for every 550 ft increase in altitude






• In Denver, Colorado (altitude 5,280 ft), water boils at 202°F




Pressure CapsPressure Caps• Metric Radiator Caps

– All radiator caps indicate their normal pressure rating

– Most original equipment radiator caps rated at 14 to 16 PSI (97 to 110kPa)





– Many vehicles from Japan and Europe measure pressure in unit called bar

– One bar is about 14.7 PSI




Chart 21-2 Comparison showing the metric pressure as shown on the top of the cap to pounds per square inch (PSI).





– NOTE: Many radiator repair shops use 7PSI (0.5bar) radiator caps.

• A 7 PSI cap provides boil protection of 21°F (3°F × 7 PSI = 21°F) above boiling point






• The coolant can still boil before the “hot” dash warning light comes on






• Lower boil point can cause cavitation and damage water pump






• Always follow vehicle manufacturer’s recommended radiator cap




COOLANT RECOVERYCOOLANT RECOVERYSYSTEMSSYSTEMS




Coolant Recovery SystemsCoolant Recovery Systems• Purpose and Function

– Excess pressure causes coolant to overflow– Most cooling systems connect to plastic

reservoir to hold excess coolant




Figure 21-15 The level in the coolant recovery system raises and lowers with engine temperature.





– When system cools, pressure is reduced creating partial vacuum

– Vacuum pulls coolant from reservoir back into cooling system





– System called coolant recovery system




Coolant Recovery SystemsCoolant Recovery Systems• Surge Tank

– Some vehicles use surge tank– Surge tank located at highest level of

cooling system





– Surge tank holds about 1 quart (1 liter) of coolant

– Hose attaches bottom of surge tank to inlet side of water pump





– Smaller bleed hose attaches side of surge tank to highest point of radiator

– Bleed line allows some coolant circulation through surge tank





– Air is forced from system if pressure exceeds rating of radiator cap




Figure 21-16 Some vehicles use a surge tank, which is located at the highest level of the cooling system, with a radiator cap.




WATER PUMPSWATER PUMPS




Water PumpsWater Pumps• Operation

– Water pump is driven by one of two methods:

• Crankshaft belt• Camshaft





– Coolant recirculates from radiator to engine and back to radiator

– Low-temperature coolant leaves radiator by bottom outlet





– Coolant flows to engine block and then to cylinder heads

– NOTE: Some engines use reverse-cooling. Coolant flows from radiator to cylinder heads before flowing to engine block.





– Water pump is not positive displacement pump

– Water pump is centrifugal pump





– Pump pulls coolant in at the center of the impeller

– Centrifugal force throws coolant outward to be discharged at impeller tips

?




Figure 21-17 Coolant flow through the impeller and scroll of a coolant pump for a V-type engine.





– Higher engine speeds produce more heat– Pump impeller speed increases with engine

speed





– Coolant leaving pump impeller feeds through a scroll

– Scroll connects to front of engine to direct coolant into engine block





– On V-type engines, two outlets are often used

– Occasionally, diverts are needed to equalize coolant flow between engine banks




Water PumpsWater Pumps• Water Pump Service

– Worn impeller can reduce amount of coolant flow

– If water pump seal fails, coolant will leak from weep hole




Figure 21-19 This severely corroded water pump could not circulate enough coolant to keep the engine cool. As a result, the engine overheated and blew a head gasket.





– Weep hole allows coolant to escape– Defective bearing is noisy and must be

replaced




Figure 21-20 The bleed weep hole in the water pump allows coolant to leak out of the pump and not be forced into the bearing. If the bearing failed, more serious damage could result.





– Before replacing water pump because of noisy bearing, check

• Drive belt tension• Bent fan





– Before replacing water pump because of noisy bearing, check

• Fan for balance





– If pump drive belt is too tight, excessive force may be exerted on pump bearing





– If cooling fan is bent or out of balance, vibration can damage pump bearing




Figure 21-21 A cutaway of a typical water pump showing the long bearing assembly and the seal. The weep hole is located between the seal and the bearing. If the seal fails, then coolant flows out of the weep hole to prevent the coolant from damaging the bearing.




COOLANT FLOWCOOLANT FLOWIN THE ENGINEIN THE ENGINE




Coolant Flow in the EngineCoolant Flow in the Engine• Types of Systems

– Coolant flows through engine in one of following ways

• Parallel flow system– Coolant flows into block under pressure and

then crosses the head gasket to the head through main coolant passages beside each cylinder






• Series flow system– Coolant flows around cylinders on each bank






• Series flow system– Coolant flows to rear of block where coolant

flows across head gasket






• Series flow system– Coolant then enters rear of heads






• Series flow system– In heads, coolant flows forward to crossover

passage on intake manifold outlet at highest point in engine cooling passage






• Series-parallel flow system– Combination of series-flow and parallel-flow

systems






• Series-parallel flow system– Any stem goes directly to top of radiator






• Series-parallel flow system– Bleed holes or steam slits let out the steam




Coolant Flow in the EngineCoolant Flow in the Engine• Coolant Flow and Head Gasket Design

– Most but not all V-type engines use cylinder heads that are interchangeable side to side




Coolant Flow in the EngineCoolant Flow in the Engine• Coolant Flow and Head Gasket Design

– Double check that cylinder head is matched to block and that head gasket is installed correctly




Figure 21-22 A Chevrolet V-8 block that shows the large coolant holes and the smaller gas vent or bleed holes that must match the head gasket when the engine is assembled.




COOLING FANSCOOLING FANS




Cooling FansCooling Fans• Electronically Controlled Cooling Fan

– Two Types• One two-speed cooling fan





– Two Types• Two cooling fans (one for normal cooling;

one for high heat conditions)





– PCM commands low-speed fans under these conditions

• ECT exceeds approximately 223°F (106°C)






• A/C refrigerant pressure exceeds 190 PSI (1,310 kPa)






• After engine is shut off, coolant temperature is greater than 284°F (140°C) and system voltage is more than 12 volts.





– PCM commands the high-speed fan under these conditions

• ECT reaches 230°F (110°C)






• A/C refrigerant pressure exceeds 240 PSI (1,655 kPa)






• Certain DTCs set





– To prevent excessive fan cycling, fan may not turn off until ignition is turned off or vehicle speed exceeds 10 mph (16km/h)





– Many rear-wheel-drive vehicles and all transverse engines drive the fan with an electric motor




Figure 21-23 A typical electric cooling fan assembly showing the radiator and related components.





– NOTE: Most electric cooling fans are computer controlled. Most are turned off when vehicle exceeds 35 mph (55 km/h). Ram air keeps radiator cool. If computer senses temperature is too high, computer turns on cooling fan.




Cooling FansCooling Fans• Thermostatic Fans

– On some rear-wheel-drive vehicles, a thermostatic cooling fan is driven by a belt from the crankshaft





– The cooling systems transfers more heat at higher speeds





– Two Types of Thermostatic Fans:• Silicone coupling: fan drive is mounted

between drive pulley and fan– HINT: When diagnosing overheating, examine

cooling fan. If silicone is leaking, fan may not function correctly.





– Two Types of Thermostatic Fans:• Thermostatic spring: thermostatic spring

added to silicone coupling fan drive– Thermostatic spring operates valve that

allows fan to freewheel when radiator is cold





– Two Types of Thermostatic Fans:• Thermostatic spring: thermostatic spring

added to silicone coupling fan drive– When radiator warms to 150°F (65°C), spring

opens valve that allows drive to operate like silicone coupling drive




Figure 21-24 A typical engine-driven thermostatic spring cooling fan.




HEATER CORESHEATER CORES




Heater CoresHeater Cores• Purpose and Function

– Some heat absorbed by cooling system passes through tubes to small core of the heater




Heater CoresHeater Cores• Purpose and Function

– Air passes across heater fends and sent to passenger compartment




Figure 21-25 A typical heater core installed in a heating, ventilation, and air-conditioning (HVAC) housing assembly.




Heater CoresHeater Cores• Heater Problem Diagnosis

– To find cause of lack of heat to heater follow these steps





– Step 1: Feel upper radiator hose; it should be too hot to hold; it should have pressure.

• If hose is not hot, replace thermostat.






• If hose is not pressurized, test or replace radiator pressure cap.






• If okay, see step 2.





– Step 2: With engine running, feel both heater hoses. Both should be too hot to hold.

• If hoses are warm or cool, check heater control valve.





– Step 2: With engine running, feel both heater hoses. Both should be too hot to hold.

• If one hose is hot and other warm or cool, remove hoses and flush heater core.





– Step 3: If both hoses are hot but heat is insufficient, check for airflow blend door malfunction.




Heater CoresHeater Cores• HINT: Heat from heater that comes and

goes is likely the result of low coolant level. It may work at lower engine speeds but not at higher speeds.




COOLING SYSTEM COOLING SYSTEM TESTINGTESTING




Cooling System TestingCooling System Testing• Visual Inspection

– Many faults can be identified with visual inspection

• Water pump drive belt for tension or faults






• Cooling fan for faults






• Heater and radiator hoses for condition and leaks






• Coolant overflow or surge tank coolant level






• Evidence of coolant loss






• Radiator condition




Figure 21-26 A heavily corroded radiator from a vehicle that was overheating. A visual inspection discovered that the corrosion had eaten away many of the cooling fins, yet did not leak. This radiator was replaced and it solved the overheating problem.




Cooling System TestingCooling System Testing• Pressure Testing

– Using hand-operated pressure tester, remove radiator cap

– Operating plunger on pump pressurizes cooling system




Figure 21-27 Pressure testing the cooling system. A typical handoperated pressure tester applies pressure equal to the radiator cap pressure. The pressure should hold; if it drops, this indicates a leak somewhere in the cooling system. An adapter is used to attach the pump to the cap to determine if the radiator can hold pressure, and release it when pressure rises above its maximum rated pressure setting.





– CAUTION: Do not pump up pressure beyond that specified by vehicle manufacturer, usually 14 PSI (100 kPa).





– If system is free from leaks, pressure will stay and not drop





– If pressure drops check for leaks• Heater hoses• Radiator hoses





– If pressure drops check for leaks• Radiator• Heater core





– If pressure drops check for leaks• Cylinder head• Core plugs in block or cylinder head





– Perform pressure testing whenever there is leak or suspected leak

– Pressure tester can also be used to test radiator cap




Figure 21-28 The pressure cap should be checked for proper operation using a pressure tester as part of the cooling system diagnosis.




Cooling System TestingCooling System Testing• Coolant Dye Leak Testing

– Use fluorescent dye in coolant– Operate vehicle to reach normal operating

temperature




Cooling System TestingCooling System Testing• Coolant Dye Leak Testing

– Use black light to inspect cooling system




Figure 21-29 Use dye specifically made for coolant when checking for leaks using a black light.




COOLANT COOLANT TEMPERATURETEMPERATURE

WARNING LIGHTWARNING LIGHT




Coolant Temperature Warning LightCoolant Temperature Warning Light• Purpose and Function

– Most vehicles have heat sensor to engine operating temperature indicator light




Coolant Temperature Warning LightCoolant Temperature Warning Light• Purpose and Function

– If light comes on (or temperature gauge goes into red danger zone) coolant is 250°F to 258°F (120°C to 126°C)




Figure 21-30 When an engine overheats, often the coolant overflow container boils.




Coolant Temperature Warning LightCoolant Temperature Warning Light• Precautions

– If coolant temperature warning light comes on, follow these steps

• Step 1: Shut off air conditioning and turn on heater. Set blower speed to high.






• Step 2: Shut engine off and let it cool.• Step 3: Do not remove radiator cap while

engine is hot.






• Step 4: Do not continue to drive.• Step 5: If engine does not feel or smell hot,

problem may be faulty hot light sensor or gauge.




Coolant Temperature Warning LightCoolant Temperature Warning Light• Common Causes of Overheating

– Low coolant level– Plugged, dirty, or blocked radiator





– Defective fan clutch or electric fan– Incorrect ignition timing (if adjustable)





– Low engine oil level– Broken fan drive belt





– Defective radiator cap– Dragging brakes





– Frozen coolant (in freezing weather)– Defective thermostat





– Defective water pump (impeller slipping on internal shaft)

– Blocked cooling passages in block or cylinder head(s)




COOLING SYSTEMCOOLING SYSTEMINSPECTIONINSPECTION




Cooling System InspectionCooling System Inspection• Coolant Level

– Normal maintenance involves checking coolant level and visual inspection for leaks and condition of hoses and belts




Cooling System InspectionCooling System Inspection• Coolant Level

– CAUTION: Check coolant only when engine is cool. Removing pressure cap from hot engine will cause coolant to boil immediately. Vapors will blow coolant from system. Coolant will be lost; someone may be injured.




Cooling System InspectionCooling System Inspection• Accessory Drive Belt Tension

– Four ways manufacturers specific belt tension is within specifications1. Belt tension gauge

– Install belt and operate engine for five minutes






– Adjust tension to factory specifications or use Chart 21-3




Chart 21-3 The number of ribs determines the tension range of the belt.






– Replace serpentine belt with more than three cracks in 3 in. span





– Four ways manufacturers specific belt tension is within specifications2. Marks on tensioner

– Many tensioners have marks indicating normal operating tension range





– Four ways manufacturers specific belt tension is within specifications2. Marks on tensioner

– Check service information for location of tensioner mark




Figure 21-31 Typical marks on an accessory drive belt tensioner.





– Four ways manufacturers specific belt tension is within specifications3. Torque wrench reading

– Some manufacturers specify use of beam-type torque wrench





– Four ways manufacturers specific belt tension is within specifications4. Deflection

– Depress belt between the two pulleys that are farthest apart





– Four ways manufacturers specific belt tension is within specifications4. Deflection

– Deflection should be 1/2 in.




COOLING SYSTEMCOOLING SYSTEMSERVICESERVICE




Cooling System ServiceCooling System Service• Flushing Coolant

– Step 1: Drain system.– Step 2: Fill system with clean water and

flushing/cleaning chemical.





– Step 3: Start engine; run until it reaches operating temperature with heater on.

– Step 4: Drain system and fill with water.





– Step 5: Repeat until drain water runs clear.– Step 6: Fill system with 50/50

antifreeze/water mix or premixed coolant.





– Step 7: Run engine until it reaches operating temperature with heater on.

– Step 8: Adjust coolant level as needed.





– Bleed air from cooling system• Attach clear hose to bleeder valve; put other

end in container





– Bleed air from cooling system• Check service information for specific

bleeding procedures and location of bleeder fittings




Figure 21-32 (a) Many vehicle manufacturers recommend that the bleeder valve be opened whenever refilling the cooling system.




Figure 21-32 (b) Chrysler recommends that a clear plastic hose (1/4 in. ID) be attached to the bleeder valve and directed into a suitable container to keep from spilling coolant onto the ground and on the engine and to allow the technician to observe the flow of coolant for any remaining oil bubbles.




Cooling System ServiceCooling System Service• Coolant Exchange Machine

– Many coolant exchange machines can perform one of more of these operations

• Exchange old coolant with new coolant






• Flush cooling system






• Pressure or vacuum check system for leaks





– Exchange machine helps eliminate air pockets





– Air pockets show these symptoms• Lack of heat from heater





– Air pockets show these symptoms• Overheating




Figure 21-33 Using a coolant exchange machine helps eliminate the problem of air getting into the system which can cause overheating or lack of heat due to air pockets getting trapped in the system.




Cooling System ServiceCooling System Service• Hose Inspection

– A hose should be replaced any time it appears abnormal




Figure 21-34 All cooling system hoses should be checked for wear or damage.





– HINT: To make hose removal easier and to avoid damage to radiator, slit hose lengthwise with utility knife. Peel hose off.





– Position hose and hose clam so clamp is close to the bead on the neck




Cooling System ServiceCooling System Service• Disposing of Used Coolant

– Dispose of coolant according to state or local laws

– Some communities allow draining into sewer




Cooling System ServiceCooling System Service• Disposing of Used Coolant

– Groundwater contamination can occur if coolant is spilled on ground

– Check with recycling companies for recommended disposal methods




Cooling System ServiceCooling System Service• Cleaning the Radiator Exterior

– Overheating can result from exterior and interior radiator plugging




Cooling System ServiceCooling System Service• Cleaning the Radiator Exterior

– Exterior plugging can be seen if you look through the radiator

– Exterior can be cleaned with water pressure from hose

halderman ch021 lecture

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