(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 Diagnostics

Cooling-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 LeaksExternal leaks

most 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

Cooling System Problems

Mineral deposits in water jackets can

prevent proper heat transfer

Cooling System Problems

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

Cooling System Pressure Tester

One of the most commonly used and important cooling system testing devices!

Cooling System Pressure Test

TO AVOID SERIOUS BURNS,TO AVOID SERIOUS BURNS, NEVER NEVER REMOVE A RADIATOR CAP WHEN REMOVE A RADIATOR CAP WHEN

ENGINE IS HOT!ENGINE IS HOT!Install pressure tester on filler neckPump the tester to pressurize systemUse cap rating for maximum psi to avoid serious Use cap rating for maximum psi to avoid serious

damage to cooling systemdamage to cooling systemLow air pressure is forced into the system

causes coolant to pour or drip from any leak

Combustion Leak Combustion Leak TestTest 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, If combustion gases are present in the radiator,

fluid changes color (from blue to yellow)fluid changes color (from blue to yellow)

Combustion Leak Test

Combustion leakage Combustion leakage can makecan make

the engine overheatthe engine overheat

Combustion Leak TestLeak testing with an exhaust gas

analyzer. HC reading indicates leakage

Causes of Causes of OverheatingOverheatingLow coolant level

Rust or scale accumulation in coolantRust or scale accumulation in coolantStuck thermostatRetarded ignitionLoose fan/water pump beltLoose fan/water pump beltBad water pump Collapsed lower hoseCollapsed lower hoseMissing fan shroud or fan problems Ice in the coolantIce in the coolant

Causes of Overcooling

Stuck thermostat (open)Locked fan clutchShorted fan switch

Indications of Overcooling

Heater does not get hotHeater does not get hotTemperature gage remains coldTemperature gage remains coldPoor fuel economyPoor 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

Common Causes of Water Pump Failure:rust in the cooling systemrust in the cooling systemlack of coolantlack of coolantovertightened beltsovertightened belts

Visual Inspection(Checking for worn Water Pump

Bearings)

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

Visual Inspection

Watch for leakage from bleed holesA mechanic’s stethoscopemechanic’s stethoscope can be used to

pinpoint failing water pump bearings

Removing a Water Pump

Unbolt brackets and componentsair-conditioning compressorpower steering pumpalternator

Remove pump Scrape off old gasket or sealer material Do not use excessive force when separating Do not use excessive force when separating

a water pump from an engine because you a water pump from an engine because you may gouge the sealing surfaces!may gouge the sealing surfaces!

Installing a New Water Pump

(Most Technicians prefer to install a new water pump rather (Most Technicians prefer to install a new water pump rather than rebuilding the old one, because it is more cost effective than rebuilding the old one, because it is more cost effective

and comes with a better warranty)and comes with a better warranty) Fit pump onto the engine Start all bolts by hand Torque all fasteners to specifications Use sealer where specified Install the other components

Installing a Water Pump

A. Gasket held in place by sealer

B. Sealer only

Note: Be sure to use the correct sealer to adhere the Note: Be sure to use the correct sealer to adhere the water pump gasket to the water pump to avoid coolant water pump gasket to the water pump to avoid coolant

leakageleakage

Water Pump

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

Installation

Tightening water pump bolts evenly to proper torque specs

Water Pump Components

A stuck thermostat can cause engine A stuck thermostat can cause engine overheating or overcoolingoverheating or overcooling

Stuck open–overcoolingloss of efficiency, power, mileagehigh emissions

Stuck closed–overheatingengine damage

Thermostat Testing Watch the coolant through the opening in the

radiator neck Cold engine, coolant should not flow Hot engine, coolant should begin to circulate past

the opening Use a digital thermometer to monitor the Use a digital thermometer to monitor the

temperature of the thermostat housing and outlet temperature of the thermostat housing and outlet hose. If the housing is reaching engine operating hose. If the housing is reaching engine operating temperature but the outlet hose stays cool, the temperature but the outlet hose stays cool, the thermostat is not opening and needs to be replacedthermostat is not opening and needs to be replaced

Thermostat and Housing

Caution: Over tightening the thermostat housing can Caution: Over tightening the thermostat housing can cause it to warp or crack and create coolant leakagecause it to warp or crack and create coolant leakage

Thermostat Replacement

Thermostat and Housing

Some manufacturers use an O-ring seal which should Some manufacturers use an O-ring seal which should be replaced anytime the thermostat is removedbe replaced anytime the thermostat is removed

Bleeding the Cooling System

A bleed valvebleed valve is sometimes provided to help eliminate trapped air in the cooling system

Cars with low hood lines require a bleed screw to empty air pockets

Trapped air can cause overheating or a buildup of heat called a hot spothot spot

Bleeding 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 Never remove a cooling system

bleed screw or any clamp on a hot, bleed screw or any clamp on a hot, pressurized system!pressurized system!

Hoses deteriorate and become Hoses deteriorate and become soft and mushy or hard and brittle soft and mushy or hard and brittle

and should be replacedand should be replaced

Common Hose

Problems

Hose ReplacementA.A. Loosen clamp, Loosen clamp, B.B. Twist and pull hose offTwist and pull hose offC.C. Clean fittingClean fittingD.D. Install new hose and clampInstall new hose and clampE.E. Check for leaksCheck for leaks

Inspecting the Radiator and Pressure

CapConditions that can limit airflow through the Conditions that can limit airflow through the

radiator radiator Inspect radiator fins for debris and rot Make sure the shroud is in place

Perform a Radiator Cap Pressure TestRadiator Cap Pressure Testwhich measures cap opening pressurechecks sealing washer conditionTO AVOID SERIOUS BURNS,TO AVOID SERIOUS BURNS, NEVER REMOVE NEVER REMOVE

A RADIATOR CAP WHEN ENGINE IS HOT!A RADIATOR CAP WHEN ENGINE IS HOT!

Pressure Testing a Radiator Cap

Radiator Removal

Place a catch pan under the cool radiatorPlace a catch pan under the cool radiatorOpen the petcock to drain systemOpen the petcock to drain systemDisconnect hoses and oil cooler linesDisconnect hoses and oil cooler linesDisconnect wires going to sensors and Disconnect wires going to sensors and

fan motorsfan motorsRemove any brackets and radiatorRemove any brackets and radiator

Radiator Removal

Radiator Repair

Most repairs are done by a radiator shopRadiator shops disassemble, clean,

repair, reassemble and test radiatorsWhen installing radiator, make sure the

rubber mounts are in place

An over tightened fan/water pump belt An over tightened fan/water pump belt can causecan cause water pump bearing failure water pump bearing failure

A loose fan beltA loose fan belt will slip and squeal and will slip and squeal and may cause overheatingmay cause overheating

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

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

Check for bent blades, cracks or fluid leakage

Testing a Thermostatic Fan Clutch

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

you should hear the rush of airyou should hear the rush of air

Electric Cooling Fan

Most electric cooling system fans are controlled by a Most electric cooling system fans are controlled by a temperature switch or sensor located in the radiator, temperature switch or sensor located in the radiator, thermostat housing, or engine block.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.

Testing an Electric Cooling Fan

A. Check for power to the fan, engine hotCheck for power to the fan, engine hot

B. Switch open when cold, closed when hotSwitch open when cold, closed when hot

C. Test using a test lamp or digital volt meterdigital volt meter

Leaking freeze plugs cause coolantloss and overheating

Occasional replacement may be necessary because of corrosion

Freeze plugs are madeFreeze plugs are made thinner thinner than the than the metal in the engine block and will fail metal in the engine block and will fail much sooner than other parts of the much sooner than other parts of the engineengine

Freeze Plug

Replacement

A.A. Drive drift through plugDrive drift through plug

B.B. Pry outPry out

C.C. Clean hole Clean hole

D.D. Coat hole with sealerCoat hole with sealer

E.E. Install with driver toolInstall with driver tool

Coolant should be checked and changed at regular intervalsregular intervals (according to manufacturer’s recommendations)

Breaks down and becomes conductiveRust preventative properties are lostBoiling and freezing properties may become

compromised.

Digital Volt Meter used to check for Digital Volt Meter used to check for dissolved metals in the coolantdissolved metals in the coolant

Coolant Tester used to check the Coolant Tester used to check the boiling & freezing points of the coolantboiling & freezing points of the coolant

One of the most common causes of cracked blocks and cylinder One of the most common causes of cracked blocks and cylinder heads is water freezing and expanding in the engine from lack of heads is water freezing and expanding in the engine from lack of

coolant!coolant!

Changing Coolant

Checking Coolant Level

With recovery reservoir: Coolant should be even with correct marking on reservoir and full to top of radiator

Max

Min

Full

Checking Coolant Level

Without recovery reservoir:

Coolant should be 1” below the top

of the tank on systems without a recovery tank

Testing Coolant Strength

Measures the concentration of antifreeze compared to water

Determines freeze protectionTools used:

cooling system hydrometerrefractometer

Coolant Tester/HydrometerWhen filled, pointer will float to indicate

freeze protection

Good

Not so Good

Cleans rust and scale from the system. Cleans rust and scale from the system.

Rust (iron oxide) is very harmful to the cooling Rust (iron oxide) is very harmful to the cooling system. It can cause premature failure of the system. It can cause premature failure of the water pump, block small passages in the radiator water pump, block small passages in the radiator core, and cause electrolysis to occur.core, and cause electrolysis to occur.

May involve running a cleaning chemical through the system

Methods:fast flushingreverse flushingchemical flushing

Fast Flushing

Reverse Flushing

Reverse Reverse flushing flushing involves involves flowing air and flowing air and water water backwards to backwards to the normal the normal flow of coolant flow of coolant through the through the radiator core radiator core and engine and engine blockblock

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 includeGauge problems may include the gauge reading too hot, too the gauge reading too hot, too

cold, or not moving at allcold, or not moving at all

Gauge or Indicator Light Test

Disconnect wire from temperature sending unit

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

is grounded this indicates the gauge is is grounded this indicates the gauge is working. The sending unit may require working. The sending unit may require replacementreplacement

Check service manual before this test

Gauge TesterUsed if the gauge is suspected of being

faulty or out of calibrationSpecial device with a variable resistor variable resistor,

replaces the temperature sending unit in the temperature gauge circuit

Set tester to a specified resistanceSet tester to a specified resistanceConnect tester as in diagram on next slideConnect tester as in diagram on next slideGauge should read as specifiedGauge should read as specified

Using Gauge Tester

Gauge or IndicatorLight Test

© Goodheart-Willcox Co., Inc.

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