1. Chapter 14
Cooling System

2. Objectives Analyze wear and damage to cooling system parts
Explain cooling system theory
Select and perform most appropriate repairs to cooling system

3. Types of Cooling Systems
Smaller engines are cooled by air only
Most automotive cooling systems use liquid coolant
Engine block and cylinder head have cast-in water jackets

4. Cooling System Parts Water pump or coolant pump Radiator Radiator hose
The fan
Thermostat
Coolant

5. Coolant Pump Typically called a water pump
Impeller type pump
Mounted on front of engine and belt-driven
Aluminum or cast iron
Shaft supported by a bearing and uses a spring loaded front seal

6. Coolant Pump

7. Coolant Pump Failure Static Seal Bearing Impeller Pump plate leakage
Coolant leaks from coolant vent hole
Bearing
Will also damage static seal
Impeller
Broken pieces of impeller can enter the block, and possibly the radiator
Pump plate leakage

8. Possible Reasons for Pump Failure
High engine miles
Engine ran low on coolant
Out of balance fan assembly
Faulty fan spacer

9. Belt Materials Tensile chords provide strength
V-ribbed belts ribbed on one side and flat on the other
Thickness of v-ribbed belt allows it to wrap around smaller pulleys as well as bend backwards
This allow both sides to transmit power

10. Accessory Drive Belt Service
Check all belts for wear, cracks, or damage
Replace glazed belt
Check for proper belt alignment

11. Drive Belt Service

12. Thermostats
Allows engine to warm up and maintain a constant temperature
Made of brass or stainless steel
Expansive wax compound expands at predictable rate to open valve
Rated according to engine temperature

13. Radiators Cross flow or down flow style
Coolant flows through radiator cores
Cores are constructed from copper or aluminum
Aluminum radiator cores conduct heat better than copper
Plugged radiator will cause overheating

14. Heater Core Heat exchanger located inside passenger compartment
Heat is transferred form engine into heater core then into vehicle
Core can leak or become plugged
Constructed of aluminum, copper, or brass

15. Hoses
Consist of inner rubber tube, reinforcement, and outer rubber cover
Have a burst strength five to six times the normal operating pressure

16. Hoses
3 types
Straight
Molded
Universal

17. Cooling System Pressure Cap
Putting system under pressure raises boiling point of coolant
Each pound of pressure raises boiling point three degrees
Cap includes a valve that allows coolant back into radiator as temperature drops

18. Radiator Pressure Cap

19. Radiator Fan Draws air through radiator at idle and low speeds
Aluminum, plastic, or steel blades
Most late model vehicles use a fan driven by an electric motor
Some rear wheel drive vehicles still use belt driven fans

20. Coolant Additives Borax Phosphate Sodium molybdate Sodium silicate
Sodium nitrate
Triazoles

21. Coolant Additives
Sodium hydroxide
Phosphorescent
Benzoate
Water

22. Electrolysis Destructive to engine cooling system Three types
Chemical electrolysis
Coolant has become too acidic
Caused from dissimilar metals in cooling system
Faulty electrical ground
Static electricity

23. Checking Coolant Conductivity
Ground positive probe by grounding it to radiator
Insert negative lead into coolant
Reading should be .2 volts or less
If reading is .5 volts or more
System should be flushed and refilled with new coolant

24. Checking Coolant Conductivity

25. Testing Coolant Condition and Strength
Test strips can check pH, cavitation additive protection, and coolant concentration
Conventional coolant has a higher pH than extended coolant

26. Testing Coolant Condition and Strength
Used conventional coolant should have a pH level of at least 9
Extended life should be at least 7.5

27. Testing Coolant Condition and Strength

28. Coolant Density Testers
Two ways to test density:
Hydrometer
Compares weight of ethylene glycol to weight of pure water
Refractometer
Measures how much light can be bent by coolant

29. Coolant Density Testers

30. Coolant System Air Bleeding
All air must be removed from system
Jack front of car up as high as it will go
Some vehicles have bleed screws
Remove heater hose to bleed air
Use special air removal tool

31. Cavitation Causes of formation of air bubbles in coolant
Coolant boiling
Air in coolant
Suction restriction
Over pumping
Vibration of cylinder wall during combustion