Cooling System

1
Cooling System Testing, Maintenance, and Repair
Chapter 40
2
Contents
(12 Topics)

• Cooling system diagnosis
• Cooling system problems
• Water pump service
• Thermostat service
• Cooling system hose service
• Radiator and pressure cap service

3
Contents

• Fan belt service
• Engine fan service
• Freeze plug service
• Coolant service
• Flushing a cooling system
• Temperature gauge service

4
Cooling System Problem Diagnosis

• Gather information
• Talk to the owner or service writer to find out
  as much as possible about the symptoms
• A Cooling System Diagnosis Chart in the service
  manual can be very helpful when problems are
  difficult to locate and correct.

5
On-Board Diagnostics

• Cooling-related problems may set a diagnostic
  trouble code on some systems if temperatures seem
  out of range.
• use a scan tool to analyze the system
• MIL lamp may be on
• data will indicate engine temperature
• even failure to bleed a system of air could cause
  erratic temperature sensing

6
Cooling System Functions often monitored by the
OBD II system

• Coolant Temperature
• Engine oil Temperature
• Belt Tension
• Other related functions

7
Visual Inspection of Cooling System

• Perform a visual inspection for
• coolant leaks
• loose or missing fan belts
• low coolant level
• water pump noises
• plugged radiator fins
• coolant in the oil (oil looks milky)
• combustion leakage into coolant

8
Common Problems
9
Cooling System Problems

• Coolant leaks
• Overheating
• Overcooling

10
Coolant Leaks

• External leaks
• most common
• show up as wet, discolored areas on parts
• Internal leaks
• caused by cracked block, head or blown head gasket

11
Cooling System Problems

• A blown head gasket can allow combustion gases
  to enter the coolant, a combustion leak test will
  verify this type of problem

12
Cooling System Problems

• Mineral deposits in water jackets can prevent
  proper heat transfer

13
Cooling 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

14
Cooling System Pressure Tester
One of the most commonly used and important
cooling system testing devices!
15
Cooling System Pressure Test

• TO AVOID SERIOUS BURNS, NEVER REMOVE A RADIATOR
  CAP WHEN ENGINE IS HOT!
• Install pressure tester on filler neck
• Pump the tester to pressurize system
• Use cap rating for maximum psi to avoid serious
  damage to cooling system
• Low air pressure is forced into the system
• causes coolant to pour or drip from any leak

16
Combustion 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 (from blue to yellow)

17
Combustion Leak Test

• Combustion leakage can makethe engine overheat

18
Combustion Leak Test

• Leak testing with an exhaust gas analyzer. HC
  reading indicates leakage

19
Causes of Overheating

• Low coolant level
• Rust or scale accumulation in coolant
• Stuck thermostat
• Retarded ignition
• Loose fan/water pump belt
• Bad water pump
• Collapsed lower hose
• Missing fan shroud or fan problems
• Ice in the coolant

20
Causes of Overcooling

• Stuck thermostat (open)
• Locked fan clutch
• Shorted fan switch

Indications of Overcooling

• Heater does not get hot
• Temperature gage remains cold
• Poor fuel economy

21
Water Pump Service

• A bad pump may leak, fail to circulate coolant,
  or produce a grinding sound
• Common Causes of Water Pump Failure
• rust in the cooling system
• lack of coolant
• overtightened belts

22
Visual Inspection(Checking for worn Water Pump
Bearings)

• Pump shaft should not wiggle or leak

23
Visual Inspection

• Watch for leakage from bleed holesA mechanics
  stethoscope can be used to pinpoint failing
  water pump bearings

24
Removing a Water Pump

• Unbolt brackets and components
• air-conditioning compressor
• power steering pump
• alternator
• Remove pump
• Scrape off old gasket or sealer material
• Do not use excessive force when separating a
  water pump from an engine because you may gouge
  the sealing surfaces!

25
Installing 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 engine
• Start all bolts by hand
• Torque all fasteners to specifications
• Use sealer where specified
• Install the other components

26
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 water pump gasket to the water pump to avoid
coolant leakage
27
Water Pump

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

28
Installation

• Tightening water pump bolts evenly to proper
  torque specs

29
Water Pump Components
30
Thermostat Service

• A stuck thermostat can cause engine overheating
  or overcooling
• Stuck openovercooling
• loss of efficiency, power, mileage
• high emissions
• Stuck closedoverheating
• engine damage

31
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
  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

32
Thermostat and Housing
Caution Over tightening the thermostat housing
can cause it to warp or crack and create coolant
leakage
33
Thermostat Replacement
34
Thermostat and Housing

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

35
Bleeding the Cooling System

• A bleed 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 spot

36
Bleeding the Cooling System

• Fill the system
• Start and warm the engine
• Crack open the bleed screw until all air is
  purged from the system
• Never remove a cooling system bleed screw or any
  clamp on a hot, pressurized system!

37
Cooling System Hose Service

• Hoses deteriorate and become soft and mushy or
  hard and brittle and should be replaced

38
Common Hose Problems
39
Hose Replacement

1. Loosen clamp,
2. Twist and pull hose off
3. Clean fitting
4. Install new hose and clamp
5. Check for leaks

40
Radiator and Pressure Cap Service
41
Inspecting the Radiator and Pressure Cap

• Conditions that can limit airflow through the
  radiator
• Inspect radiator fins for debris and rot
• Make sure the shroud is in place
• Perform a Radiator Cap Pressure Testwhich
  measures cap opening pressure
• checks sealing washer condition
• TO AVOID SERIOUS BURNS, NEVER REMOVE A RADIATOR
  CAP WHEN ENGINE IS HOT!

42
Pressure Testing a Radiator Cap
43
Radiator Removal

• Place a catch pan under the cool radiator
• Open the petcock to drain system
• Disconnect hoses and oil cooler lines
• Disconnect wires going to sensors and fan motors
• Remove any brackets and radiator

44
Radiator Removal
45
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

46
Fan Belt Service

• An over tightened fan/water pump belt can cause
  water pump bearing failure
• A loose fan belt will slip and squeal and may
  cause overheating
• Inspect the condition and tension
• Use a belt tension gauge to adjust belts

47
Engine Fan Service

• A faulty fan can cause overheating, overcooling,
  vibration and water pump damage
• Check for bent blades, cracks or fluid leakage

48
Testing a Thermostatic Fan Clutch

• Start the engine
• When cold, fan should slip
• When warm, clutch should engage
• you should hear the rush of air

49
Electric Cooling Fan

• Most 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.

50
Testing an Electric Cooling Fan

• A. Check for power to the fan, engine hot
• B. Switch open when cold, closed when hot
• C. Test using a test lamp or digital volt meter

51
Freeze Plug Service

• Leaking freeze plugs cause coolantloss and
  overheating
• Occasional replacement may be necessary because
  of corrosion
• Freeze plugs are made thinner than the metal in
  the engine block and will fail much sooner than
  other parts of the engine

52
Freeze Plug Replacement

1. Drive drift through plug
2. Pry out
3. Clean hole
4. Coat hole with sealer
5. Install with driver tool

53
Coolant Service

• Coolant should be checked and changed at regular
  intervals (according to manufacturers
  recommendations)
• Breaks down and becomes conductive
• Rust preventative properties are lost
• Boiling and freezing properties may become
  compromised.

54
Coolant Service

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

Coolant Tester used to check the boiling
freezing points of the coolant
One of the most common causes of cracked blocks
and cylinder heads is water freezing and
expanding in the engine from lack of coolant!
55
Changing Coolant
56
Checking Coolant Level

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

Max
Full
Min
57
Checking Coolant Level

• Without recovery reservoir
• Coolant should be 1 below the topof the tank on
  systems without a recovery tank

58
Testing Coolant Strength

• Measures the concentration of antifreeze compared
  to water
• Determines freeze protection
• Tools used
• cooling system hydrometer
• refractometer

59
Coolant Tester/Hydrometer

• When filled, pointer will float to indicate
  freeze protection

Good
Not so Good
60
Flushing 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 system
• Methods
• fast flushing
• reverse flushing
• chemical flushing

61
Fast Flushing
62
Reverse Flushing
Reverse flushing involves flowing air and water
backwards to the normal flow of coolant through
the radiator core and engine block
63
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

64
Temperature Gauge Service

• Gauge problems may include the gauge reading too
  hot, too cold, or not moving at all

65
Gauge or Indicator Light Test

• Disconnect wire from temperature sending unit
• Turn key on, ground wire
• If gauge sweeps or light glows as wire is
  grounded this indicates the gauge is working. The
  sending unit may require replacement
• Check service manual before this test

66
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 resistance
• Connect tester as in diagram on next slide
• Gauge should read as specified

Using Gauge Tester
67
Gauge or IndicatorLight Test
68
Questions?

• Refer to Duffy textbook chapter 40
• Scroll back through power-point
• Ask fellow student for help
• After following all the above steps, check with
  your instructor