© Goodheart-Willcox Co., Inc. (12 Topics) Cooling system diagnosis Cooling system problems Water pump service Thermostat service Cooling system

© Goodheart-Willcox Co., Inc.


(12 Topics)

Cooling system diagnosisCooling system problemsWater pump serviceThermostat serviceCooling system hose serviceRadiator and pressure cap service


Fan belt serviceEngine fan serviceFreeze plug serviceCoolant serviceFlushing a cooling systemTemperature gauge service


Gather information:Talk to the owner or service writer to find out as

much as possible about the symptomsA Cooling System Diagnosis ChartCooling System Diagnosis Chart in the

service manual can be very helpful when problems are difficult to locate and correct.


On-Board DiagnosticsCooling-related problems may set a

diagnostic trouble codetrouble 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


Cooling System Functions often monitored by the

OBD II system:Coolant TemperatureCoolant TemperatureEngine oil TemperatureEngine oil TemperatureBelt TensionBelt TensionOther related functionsOther related functions


Visual Inspection of Cooling System

Perform a visual inspection for:coolant leakscoolant leaksloose or missing fan beltsloose or missing fan beltslow coolant levellow coolant levelwater pump noiseswater pump noisesplugged radiator finsplugged radiator finscoolant in the oil (oil looks milky)coolant in the oil (oil looks milky)combustion leakage into coolantcombustion leakage into coolant


Common Problems


Coolant leaksOverheatingOvercooling


Coolant Leaks

External leaksmost commonshow up as wet, discolored areas on partsshow up as wet, discolored areas on parts

Internal leakscaused by cracked block, head or blown

head gasket


Cooling System Problems

A blown head gasket can allow combustion

gases to enter the coolant, a combustion a combustion leak test will verify this leak test will verify this

type of problemtype of problem



Mineral deposits in water jackets can

prevent proper heat transfer



A cracked part or blown gasket can

allow coolant to leak into the engine oil and

cause a milky white cause a milky white substance to form in substance to form in

the valve coversthe valve covers



Pressure Testing a Radiator Cap


Inspecting the Radiator andPressure Cap

Inspect radiator fins for debris and rot Make sure the shroud is in place Perform pressure cap test

TO AVOID SERIOUS BURNS,TO AVOID SERIOUS BURNS, NEVER REMOVE A NEVER REMOVE A RADIATOR CAP WHEN ENGINE IS HOT!RADIATOR CAP WHEN ENGINE IS HOT! measures cap opening pressure checks sealing washer condition


Cooling System Pressure Tester

one of the most commonly used and important cooling system testing devices


Cooling System Pressure Test

Low air pressure is forced into the systemcauses coolant to pour or drip from any leak

Install pressure tester on filler neckPump the tester to pressurize systemMaximum 14 psi, (or cap rating) to avoid Maximum 14 psi, (or cap rating) to avoid

serious damage to cooling systemserious damage to cooling system


Combustion Leak TestCombustion Leak Test Should 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 coolant

Place combustion leak tester on filler neck Start engine and squeeze tester bulb, pulling air

through test fluid If combustion gases are present in the radiator,

fluid changes color (usually from blue to yellow)


Combustion Leak Test

Combustion leakage can make

the engine overheat


Combustion Leak TestLeak testing with an exhaust gas

analyzer. HC reading indicates leakage


Radiator 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


Radiator Removal


Radiator Repair

Most repairs are done by a radiator shop

Radiator shops disassemble, clean, repair, reassemble and test radiators

When installing radiator, make sure the rubber mounts are in place


Causes of OverheatingCauses of OverheatingLow coolant levelRust or scale accumulation in coolantStuck thermostatRetarded ignitionLoose fan beltBad water pump or collapsed lower hoseMissing fan shroud or fan problemsIce in the coolant


Causes of Overcooling

Stuck thermostat (open)Locked fan clutchShorted fan switch

Symptoms of Overcooling

Heater does not get hotTemperature gage remains coldPoor fuel economy


A bad pump may leak, fail to circulate A bad pump may leak, fail to circulate coolant, or produce a grinding soundcoolant, or produce a grinding sound

Causes:rust in the cooling systemlack of coolantovertightened belts


Visual Inspection

Pump shaft should not wiggle or leakPump shaft should not wiggle or leak


Visual Inspection

Watch for leakage from bleed holes


Removing a Water Pump

Unbolt brackets and componentsair-conditioning compressorpower steering pumpalternator

Remove pumpScrape off old gasket or sealer materialDo not gouge the sealing surfaces


Installing a Water Pump

Fit pump onto the engineStart all bolts by handTorque all fasteners to specificationsUse sealer where specifiedInstall the other components


Installing a Water Pump

A. Gasket held in place by sealer

B. Sealer only


Water Pump

This pump uses an O-ring sealinstead of sealer or gasket


Installation

Tightening water pump bolts


Water Pump Components


A stuck thermostat can cause engine overheating or overcooling

Stuck open–overcoolingloss of efficiency, power, mileagehigh emissions

Stuck closed–overheatingengine damage


Thermostat 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


Thermostat and Housing


Thermostat Replacement


Thermostat and Housing

Special O-ring seal should be replaced anytime the thermostat is removed


Bleeding the Cooling System

A bleed valve is sometimes providedCars with low hood lines require a bleed

screw to empty air pocketsTrapped air can cause overheating or

damage from hot spots (buildup of heat)



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




Hoses deteriorate and become soft and mushy or hard and brittle


Common Hose

Problems


Hose ReplacementA. Loosen clamp, twist and pull hose offB. Clean fittingC. Install new hose and clamp, check for

leaks


A loose fan belt will slip and squealmay cause overheating

Inspect the condition and tensionUse a belt tension gauge to adjust belts


A faulty fan can cause overheating, overcooling, vibration and water pump damage

Check for bent blades, cracks or fluid leakage


Testing a Fan Clutch

Start the engineWhen cold, fan should slipWhen warm, clutch should engage

you should hear the rush of air


Testing an Electric Fan

A. Check for power to the fan, engine hot

B. Switch open when cold, closed when hot


Leaking freeze plugs cause coolantloss and overheating

Occasional replacement may be necessary because of corrosion


Freeze Plug Replacement

A. Drive drift through plug, pry out

B. Clean and coat hole with sealer, install


Coolant should be checked and changed at regular intervals

Breaks down and becomes acidicRust preventative properties are lost


Changing Coolant


Checking Coolant Level

Coolant should be even with correct marking on reservoir


Checking Coolant Level

Coolant should be 1” below the top

of the tank


Testing Coolant Strength

Measures the concentration of antifreeze compared to water

Determines freeze protectionTools used:

cooling system hydrometerrefractometer


HydrometerWhen filled, pointer will float to indicate

freeze protection


Refractometer


Cleans rust and scale from the systemMay involve running a cleaning

chemical through the systemMethods:

fast flushingreverse flushingchemical flushing


Fast Flushing


Reverse Flushing


Chemical Flushing

Used when scale buildup is causing overheating

Chemical cleaner is added to the coolant

Engine is operated for a specific amount of time

System is flushed with water


Gauge problems may include the gauge reading too hot, too cold, or

not moving at all


Gauge or Indicator Light Test

Disconnect wire from temperature sending unit

Turn key on, ground wireIf gauge sweeps or light glows as wire

is grounded, sender may require replacement

Check service manual before this test


Gauge or IndicatorLight Test


Gauge Tester

Used if the gauge is suspected of being faulty or out of calibration

Special device with a variable resistor, replaces the temperature sending unit in the temperature gauge circuit

Set tester to a specified resistanceGauge should read as specified

Documents

© Goodheart-Willcox Co., Inc. (12 Topics) Cooling system diagnosis Cooling system problems Water pump service Thermostat service Cooling system