1. Paper, Pen or Pencil for notes
Cooling System
Fundamentals
You will need:
Paper, Pen or Pencil for notes

2. Contents Cooling system functions Cooling system operation
Cooling system types
Basic cooling system
Closed and open cooling systems
Cooling system instrumentation
Antifreeze
Block heater

3. Cooling System
Functions

4. Cooling System Functions
Helps Engine Reach Operating Temperature Quickly
Maintains Constant Engine Operating Temperature
Removes Excess Engine Heat
Provides Heat For Warming the Passenger Area

5. Helps Engine Reach Operating Temperature Quickly
Advantages of Rapid Engine Warm-up:
Improved combustion (better fuel vaporization)
Reduced part wear
Less oil contamination
Increased fuel economy
Reduced emissions

6. Advantages of Maintaining a Proper Operating Temperature
Ensures Proper Combustion
Minimum Emissions
Maximum Performance
Maintains Optimum Fuel Economy

7. Maintains Constant Operating Temperature
Thermostat opens and closes to Maintain Temp
160 ºF to 195 ºF (Depending on thermostat)
When an engine warms to operating temperature parts expand and rapid warm-up reduces part wear
Ensures that clearances are correct

8. Removes Excess Engine Heat
On Modern Vehicles, Typical Combustion Temperatures can reach 4500 ºF (2500 ºC)
This is hot enough to melt metal parts
Cooling system removes excess heat which can cause major engine damage!

9. Air-cooled Engine
This air-cooled engine has had the cooling fan and shrouding removed for better viewing.
The shrouding directs the air-flow around the cylinders

10. Cooling Fan & Shrouding Removed for better view
Cooling System Types
Two common types:
air cooling liquid cooling
Cooling Fan & Shrouding Removed for better view

11. Air Cooling Versus Liquid Cooling

12. Air Cooling Systems
Large cylinder cooling fins and outside air remove excess heat
Cooling fins increase the surface area of the metal around the cylinder
This allows enough heat transfer to the outside air
Plastic or metal shrouds duct air onto and around the cylinder fins

13. Liquid Cooling Systems
Circulate coolant through the water jackets
Combustion heat is transferred to the coolant
Cooling system carries it out of the engine
Hot coolant flows into the radiator where heat is removed
Cooled coolant flows back into engine to repeat this process

14. Liquid Cooling Advantages
Precise temperature control
Less temperature variation
Reduced emissions
Improved heater operation

15. Heat is transferred to cylinder wall, into coolant and carried away
Liquid Cooling
Heat is transferred to cylinder wall, into coolant and carried away

16. Conventional Coolant Flow
Hot coolant flows from the cylinder head to the radiator
After being cooled in the radiator, the coolant flows back into the engine block

17. Reverse Flow Cooling
Cool coolant enters the head and hot coolant exits the block to return to the radiator
Helps keep a more uniform temperature throughout the engine
Found on high-performance engines

18. Basic Cooling System Components: Radiator Radiator Hoses Fan
Thermostat
Water Pump

19. Transfers coolant heat to the outside air
Radiator
Transfers coolant heat to the outside air

20. Radiator Types
Vertical Flow
Cross Flow

21. Radiator Hoses and Heater Hoses

22. Hoses Radiator Hoses Heater Hoses
Carry coolant between the engine water jackets and the radiator
Lower hose is exposed to water pump suction so a spring may prevent collapse
Heater Hoses
Carry hot coolant to the heater core
Smaller diameter than radiator hoses

23. Three basic types of hose clamps

24. Two basic types of radiator hoses

25. Radiator Fan
Draws air through the radiator and cools off the hot coolant passing through it.

26. Thermostat Maintains a constant engine temperature
Helps engine reach operating temperature quickly
Senses coolant temperature and controls coolant flow through the radiator
Reduces coolant flow on cold engine
Increases coolant flow on hot engine

27. A temperature-sensitive valve
Thermostat
A temperature-sensitive valve

28. Thermostat Operation Cold engine Hot engine
wax-filled pellet has contracted
spring holds valve closed
Hot engine
when heated, pellet expands
spring tension is overcome
valve opens

29. Thermostat Operation
A. Cold engine
B. Hot engine

30. Thermostat Operation
Cold engine Hot engine

31. Water Pump
A ribbed belt powers this pump which pumps coolant throughout the engine.
Crank pulley
Water pump pulley
Impeller
Ribbed belt

32. Impeller Pump
Coolant is thrown outward by centrifugal force, producing suction in the center of the pump housing. Straight impeller blades use less energy to operate.

33. Water Pump Cutaway
Water Pump Parts

34. Radiator Types Vertical Flow Cross Flow Tanks on top and bottom
Tanks on both sides

35. Transmission Oil Cooler
Often placed in the radiator on cars with automatic transmissions
Prevents transmission fluid from overheating

36. Transmission Oil Cooler
Small tank inside one of the radiator tanks

37. Water Pump Parts
Water pump housing -Iron or aluminum casting that forms the main body of the pump.
Water pump impeller -Disk with fan-like blades, the impeller spins and produces pressure and flow.
Water pump shaft -Steel shaft that transmits the turning force from the hub to the impeller.
Water pump seal -Prevents coolant leakage between pump shaft and pump housing.
Water pump bearing -Plain or ball-bearings that allow the pump shaft to spin freely in housing.
Water pump gasket -Fits between the water pump and the engine to prevent leakage.
Water pump hub -Provides a mounting place for the belt, pulley, and fan.

38. Radiator Hoses and Clamps
Radiator hoses –Carry coolant between the engine water jackets and the radiator.
Flexible hose –Has an accordion shape and can be bent to different angles.
Molded hose –Manufactured in a special shape, with bends to clear the cooling fan and other parts.
Heater hoses –Small-diameter hoses that carry coolant to the heater core.
Hose spring –Frequently used in the lower radiator hose to prevent the hose from collapsing.
Worm-drive hose clamps –Uses a worm gear that engages slots in the clamp strap to allow tightening around the hose.
Hose clamps –Hold the radiator hoses and heater hoses onto their fittings

39. Radiator Cap Seals the radiator Pressurizes the system
Relieves excess pressure
Allows coolant flow between the radiator and the coolant reservoir

40. Radiator Cap

41. Radiator Cap Vacuum Valve
Opens to allow flow back into the radiator when the coolant temperature drops. Without this valve the coolant would not flow back into the radiator and the radiator would become low on coolant and the engine would overheat.

42. Radiator Cap Pressure Valve
Spring-loaded disk
Normally, water boils at 212 ºF (100 ºC)
For each pound of pressure increase, boiling point goes up about 3 ºF (1.6 ºC)
Typical pressure:
12–16 psi
raises boiling point to 250–260 ºF (121–127 ºC)

43. Closed and Open Cooling Systems Closed cooling system
Uses an Expansion Tank
Overflow tube is routed into reservoir tank
Open cooling system
Allows excess coolant to leak onto the ground

44. Pressure Cap Operation
Hot engine
Cold engine

45. Cooling System Fans Pull air through the core of the radiator
Increase volume of air through the radiator
Driven by fan belt or electric motor

46. High rpm cause blades to flex, reducing blowing action
Flex Fan
High rpm cause blades to flex, reducing blowing action

47. Fluid Coupling Fan Clutch
Filled with silicone-based oil
Slips at higher rpm

48. Thermostatic Fan Clutch
Bimetal spring controls clutching action
Cold—clutch slips
Hot—clutch locks

49. Electric Cooling Fans
Provide cooling with an electric motor and a thermostatic switch
Use A small direct current motor to operate the cooling fan
Common on transverse-mounted engines
Save energy and increase cooling efficiency
Fans only function when needed

50. Electric Fan Operation
Cold engine
Hot engine

51. PCM-Controlled Fans When cold, ECM does not energize fan relays
After warm-up, ECM feeds current to the fan relay coils, closing relay contacts
High current flows to fans

52. Ensures that the fan pulls air through the radiator core
Radiator Shroud
Ensures that the fan pulls air through the radiator core

53. Modern Cooling Systems Use thermostats that are 195°F and higher (which is higher than older vehicles, 160°F-180°F)
Advantages
Engines that run higher coolant temperatures:
run smoother with more power
run more efficiently and use less fuel
burn much cleaner
heaters/defrosters work better

54. Thermostat Operation
Cold engine – Thermostat is closed no coolant flows through the radiator

55. Bypass Valve
Permits some circulation through the engine when the thermostat is closed

56. Blocks off the bypass at operating temperature
Bypass Thermostat
Blocks off the bypass at operating temperature
Impeller
Water pump drive pulley
Water pump housing
Thermostat
Main flow
Flow to radiator
Bypass spring
Bypass flow
Main spring

57. Thermostat Jiggle Valve
The valve allows trapped air to escape when the cooling system is flushed or opened for repairs. The trapped air is a serious problem which could prevent the thermostat from opening and create hot spots with erratic sensor behavior. The air is hard to remove without the valve. Since air rises up in water, the valve should be installed in the 12 o'clock position.

58. Temperature Warning Light
When coolant becomes too hot, a temperature sending unit (switch) in the block closes, completing a circuit and the warning light comes on, letting the driver know there is a problem.
Warning Light Circuit

59. Antifreeze Prevents winter freeze-up Prevents rust and corrosion
Composed of ethylene glycol mixed with water
Prevents winter freeze-up
Prevents rust and corrosion
Lubricates the water pump
Raises the boiling point
Lowers the freezing point

60. Antifreeze/Water Mixture A 50/50 mixture is most commonly used
Lowers coolant freezing point to -34 ºF
Raises the boiling point to 265 ºF

61. Protected with antifreeze
Corrosion Protection
Protected with antifreeze
Water only

62. Block Heater Installation
Aids engine starting in cold weather
120-volt heating element mounted in the block water jacket
Common on diesel engines
Block Heater Installation

63. Questions? Refer to Duffy textbook chapter 39
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