1. Cooling System
Testing, Maintenance,
and Repair
Chapter 40

2. Contents Cooling system diagnosis Cooling system problems
(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 Internal 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 leakage can make the engine overheat
Combustion Leak Test
Combustion leakage can make the 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. Indications of Overcooling
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 holes A mechanic’s stethoscope can be used to pinpoint failing water pump bearings

24. Removing a Water Pump Unbolt brackets and components Remove pump
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. This pump uses an O-ring seal instead of sealer or gasket
Water Pump
This pump uses an O-ring seal instead of sealer or gasket

28. Tightening water pump bolts evenly to proper torque specs
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 open–overcooling
loss of efficiency, power, mileage
high emissions
Stuck closed–overheating
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 Loosen clamp, Twist and pull hose off Clean fitting
Install new hose and clamp
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 Test which 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 coolant loss 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
Drive drift through plug
Pry out
Clean hole
Coat hole with sealer
Install with driver tool

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

54. Digital Volt Meter used to check for dissolved metals in the coolant
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 top of 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 Using 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 Indicator Light 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