1. The Cooling System

2. What does it do? Maintains a constant engine operating temperature
It removes excess combustion heat to prevent engine damage
Also speeds engine warm-up
Lubricates water pump

3. Cooling system types Liquid cooling Air cooling
Surrounds the cylinder with coolant
Is circulated through the water jackets by the water pump
No hot spots/constant temperature
Air cooling
Circulates air over cooling fins on the cylinders
Can be found on motorcycles, lawn mowers, and a few high-performance cars.
Can not maintain as constant a temp as liquid cooled engines
Lightweight/cheaper

4. Liquid cooling Advantages
More precise control of engine operating temperature
Less temperature variation inside engine
Reduced exhaust emissions because of better temperature control.
Improved heater operation to warm passengers

5. Basic Cooling system Water pump: Radiator hoses: Radiator:
Forces coolant through the engine and other system parts
Radiator hoses:
Connect the engine to the radiator
Radiator:
Transfers engine coolant heat to outside
air
Radiator cap regulates pressure

6. Basic Cooling System Fan: Thermostat: Heater:
Draws air through the radiator
Thermostat:
Controls coolant flow and engine operating temperature
Heater:
Provides warm air for passengers

7. Cooling System

8. 4 Functions of Antifreeze
Prevents winter freeze up
Prevents rust and corrosion
It provides a protective film on part surfaces.
Lubricates the water pump
Cools the engine
Antifreeze conducts heat better than water and therefore cools the engine better
Higher boiling point than water alone
Boiling point rises 3 degrees for every PSI!

9. Coolant mixture 50/50 mix is best for most conditions
Will provide protection from ice formation to about -34°C (-37°F)
Very cold climates may need higher ratios of antifreeze

10. Reaching operating temperature quickly… or else!
Poor combustion
Part wear
Oil contamination
Reduced fuel economy
Increased emissions

11. The Thermostat
Senses engine temperature and controls coolant flow through the radiator.
It reduces coolant flow when the engine is cold
It increases coolant flow when the engine is hot

12. The Thermostat
Can be located at either the coolant inlet or outlet on the engine.
Normally fits under a thermostat housing

13. Thermostat rating
Stamped on the thermostat to indicate the operating range
Normal ratings are between 180°F and 195°F (82°C and 91°C)
Higher thermostat heat ranges are used in modern autos because they reduce exhaust emissions and increase combustion efficiency

14. Thermostat Operation
When the engine is cold, the thermostat is closed and the coolant cannot circulate through the radiator.
Instead the coolant circulates around inside the engine until the engine is warm

15. Thermostat Operation
The thermostat has a wax filled pellet contained in a cylinder and piston assembly
When the thermostat is heated, the pellet expands and pushes the valve open.
Coolant then flows past the thermostat

16. Wax pellet cut away

17. Thermostat Operation
As the pellet and thermostat cool, spring tension overcomes the pellet expansion and the valve closes

18. The thermostat will open gradually as the heat melts the wax pellet
This gives a the engine a very consistent operating temperature
Usually between 180°F and 210°F

19. Testing Coolant Check water/antifreeze mix with hydrometer
Check conductivity with multimeter
Check Acidity with test strips

20. Testing with a hydrometer

21. Testing with a multimeter

22. Testing with PH strips

23. Pressure test cooling system and cap to rated PSI

24. Check water pump water pump leaks by weep hole?
water pump creates flow?
water pump makes noise?
Check Thermostat is working!

25. Chapter 40 p.730
Review Questions #1-15 p.749

26. Cooling System Quiz Why are air cooled engines used?
What is the typical radiator cap pressure?
What is a thermostat and what is its job?
Why is it important for an engine to warm up rapidly?
What is one advantage of water cooled engines over air cooled?