2Contents Cooling system diagnosis Cooling system problems (12 Topics)Cooling system diagnosisCooling system problemsWater pump serviceThermostat serviceCooling system hose serviceRadiator and pressure cap service
3Contents Fan belt service Engine fan service Freeze plug service Coolant serviceFlushing a cooling systemTemperature gauge service
4Cooling System Problem Diagnosis Gather information:Talk to the owner or service writer to find out as much as possible about the symptomsA Cooling System Diagnosis Chart in the service manual can be very helpful when problems are difficult to locate and correct.
5On-Board DiagnosticsCooling-related problems may set a diagnostic trouble code on some systems if temperatures seem out of range.use a scan tool to analyze the systemMIL lamp may be ondata will indicate engine temperatureeven failure to bleed a system of air could cause erratic temperature sensing
6Cooling System Functions often monitored by the OBD II system: Coolant TemperatureEngine oil TemperatureBelt TensionOther related functions
7Visual Inspection of Cooling System Perform a visual inspection for:coolant leaksloose or missing fan beltslow coolant levelwater pump noisesplugged radiator finscoolant in the oil (oil looks milky)combustion leakage into coolant
9Cooling System Problems Coolant leaksOverheatingOvercooling
10Coolant Leaks External leaks Internal leaks most common show up as wet, discolored areas on partsInternal leakscaused by cracked block, head or blown head gasket
11Cooling System Problems A blown head gasket can allow combustion gases to enter the coolant, a combustion leak test will verify this type of problem
12Cooling System Problems Mineral deposits in water jackets can prevent proper heat transfer
13Cooling System Problems A cracked part or blown gasket can allow coolant to leak into the engine oil and cause a milky white substance to form in the valve covers
14Cooling System Pressure Tester One of the most commonly used andimportant cooling system testing devices!
15Cooling System Pressure Test TO AVOID SERIOUS BURNS, NEVER REMOVE A RADIATOR CAP WHEN ENGINE IS HOT!Install pressure tester on filler neckPump the tester to pressurize systemUse cap rating for maximum psi to avoid serious damage to cooling systemLow air pressure is forced into the systemcauses coolant to pour or drip from any leak
16Combustion Leak TestShould be performed when indications of a blown head gasket, cracked head, or cracked block are suspected.Checks for the presence of combustion gases in the coolantPlace combustion leak tester on filler neckStart engine and squeeze tester bulb, pulling air through test fluidIf combustion gases are present in the radiator, fluid changes color (from blue to yellow)
17Combustion leakage can make the engine overheat Combustion Leak TestCombustion leakage can make the engine overheat
18Combustion Leak TestLeak testing with an exhaust gas analyzer. HC reading indicates leakage
19Causes of Overheating Low coolant level Rust or scale accumulation in coolantStuck thermostatRetarded ignitionLoose fan/water pump beltBad water pumpCollapsed lower hoseMissing fan shroud or fan problemsIce in the coolant
20Indications of Overcooling Causes of OvercoolingStuck thermostat (open)Locked fan clutchShorted fan switchIndications of OvercoolingHeater does not get hotTemperature gage remains coldPoor fuel economy
21Water Pump ServiceA bad pump may leak, fail to circulate coolant, or produce a grinding soundCommon Causes of Water Pump Failure:rust in the cooling systemlack of coolantovertightened belts
22Visual Inspection (Checking for worn Water Pump Bearings) Pump shaft should not wiggle or leak
23Visual InspectionWatch for leakage from bleed holes A mechanic’s stethoscope can be used to pinpoint failing water pump bearings
24Removing a Water Pump Unbolt brackets and components Remove pump air-conditioning compressorpower steering pumpalternatorRemove pumpScrape off old gasket or sealer materialDo not use excessive force when separating a water pump from an engine because you may gouge the sealing surfaces!
25Installing a New Water Pump (Most Technicians prefer to install a new water pump rather than rebuilding the old one, because it is more cost effective and comes with a better warranty)Fit pump onto the engineStart all bolts by handTorque all fasteners to specificationsUse sealer where specifiedInstall the other components
26Installing a Water Pump A. Gasket held in place by sealerB. Sealer onlyNote: Be sure to use the correct sealer to adhere the water pump gasket to the water pump to avoid coolant leakage
27This pump uses an O-ring seal instead of sealer or gasket Water PumpThis pump uses an O-ring seal instead of sealer or gasket
28Tightening water pump bolts evenly to proper torque specs InstallationTightening water pump bolts evenly to proper torque specs
30Thermostat ServiceA stuck thermostat can cause engine overheating or overcoolingStuck open–overcoolingloss of efficiency, power, mileagehigh emissionsStuck closed–overheatingengine damage
31Thermostat TestingWatch the coolant through the opening in the radiator neckCold engine, coolant should not flowHot engine, coolant should begin to circulate past the openingUse a digital thermometer to monitor the temperature of the thermostat housing and outlet hose. If the housing is reaching engine operating temperature but the outlet hose stays cool, the thermostat is not opening and needs to be replaced
32Thermostat and Housing Caution: Over tightening the thermostat housing can cause it to warp or crack and create coolant leakage
34Thermostat and Housing Some manufacturers use an O-ring seal which should be replaced anytime the thermostat is removed
35Bleeding the Cooling System A bleed valve is sometimes provided to help eliminate trapped air in the cooling systemCars with low hood lines require a bleed screw to empty air pocketsTrapped air can cause overheating or a buildup of heat called a hot spot
36Bleeding the Cooling System Fill the systemStart and warm the engineCrack open the bleed screw until all air is purged from the systemNever remove a cooling system bleed screw or any clamp on a hot, pressurized system!
37Cooling System Hose Service Hoses deteriorate and become soft and mushy or hard and brittle and should be replaced
41Inspecting the Radiator and Pressure Cap Conditions that can limit airflow through the radiatorInspect radiator fins for debris and rotMake sure the shroud is in placePerform a Radiator Cap Pressure Test which measures cap opening pressurechecks sealing washer conditionTO AVOID SERIOUS BURNS, NEVER REMOVE A RADIATOR CAP WHEN ENGINE IS HOT!
43Radiator Removal Place a catch pan under the cool radiator Open the petcock to drain systemDisconnect hoses and oil cooler linesDisconnect wires going to sensors and fan motorsRemove any brackets and radiator
45Radiator Repair Most repairs are done by a radiator shop Radiator shops disassemble, clean, repair, reassemble and test radiatorsWhen installing radiator, make sure the rubber mounts are in place
46Fan Belt ServiceAn over tightened fan/water pump belt can cause water pump bearing failureA loose fan belt will slip and squeal and may cause overheatingInspect the condition and tensionUse a belt tension gauge to adjust belts
47Engine Fan ServiceA faulty fan can cause overheating, overcooling, vibration and water pump damageCheck for bent blades, cracks or fluid leakage
48Testing a Thermostatic Fan Clutch Start the engineWhen cold, fan should slipWhen warm, clutch should engageyou should hear the rush of air
49Electric Cooling FanMost electric cooling system fans are controlled by a temperature switch or sensor located in the radiator, thermostat housing, or engine block.When the engine is cold, the fan stays off, which saves on fuel and helps the engine warm-up more quickly.When the engine is warm the fan only comes on when necessary, which also helps improve fuel economy.
50Testing an Electric Cooling Fan A. Check for power to the fan, engine hotB. Switch open when cold, closed when hotC. Test using a test lamp or digital volt meter
51Freeze Plug ServiceLeaking freeze plugs cause coolant loss and overheatingOccasional replacement may be necessary because of corrosionFreeze plugs are made thinner than the metal in the engine block and will fail much sooner than other parts of the engine
52Freeze Plug Replacement Drive drift through plugPry outClean holeCoat hole with sealerInstall with driver tool
53Coolant ServiceCoolant should be checked and changed at regular intervals (according to manufacturer’s recommendations)Breaks down and becomes conductiveRust preventative properties are lostBoiling and freezing properties may become compromised.
54Digital Volt Meter used to check for dissolved metals in the coolant Coolant ServiceDigital Volt Meter used to check for dissolved metals in the coolantCoolant Tester used to check the boiling & freezing points of the coolantOne of the most common causes of cracked blocks and cylinder heads is water freezing and expanding in the engine from lack of coolant!
56Checking Coolant Level With recovery reservoir: Coolant should be even with correct marking on reservoir and full to top of radiatorMaxFullMin
57Checking Coolant Level Without recovery reservoir:Coolant should be 1” below the top of the tank on systems without a recovery tank
58Testing Coolant Strength Measures the concentration of antifreeze compared to waterDetermines freeze protectionTools used:cooling system hydrometerrefractometer
59Coolant Tester/Hydrometer When filled, pointer will float to indicate freeze protectionGoodNot so Good
60Flushing a Cooling System Cleans rust and scale from the system.Rust (iron oxide) is very harmful to the cooling system. It can cause premature failure of the water pump, block small passages in the radiator core, and cause electrolysis to occur.May involve running a cleaning chemical through the systemMethods:fast flushingreverse flushingchemical flushing
62Reverse FlushingReverse flushing involves flowing air and water backwards to the normal flow of coolant through the radiator core and engine block
63Chemical Flushing Used when scale buildup is causing overheating Chemical cleaner is added to the coolantEngine is operated for a specific amount of timeSystem is flushed with water
64Temperature Gauge Service Gauge problems may include the gauge reading too hot, too cold, or not moving at all
65Gauge or Indicator Light Test Disconnect wire from temperature sending unitTurn key on, ground wireIf gauge sweeps or light glows as wire is grounded this indicates the gauge is working. The sending unit may require replacementCheck service manual before this test
66Gauge Tester Using Gauge Tester Used if the gauge is suspected of being faulty or out of calibrationSpecial device with a variable resistor, replaces the temperature sending unit in the temperature gauge circuitSet tester to a specified resistanceConnect tester as in diagram on next slideGauge should read as specifiedUsing Gauge Tester