The sixth lesson in our series of free auto repair classes explains details about the cooling system. Learn the parts of the cooling system, the importance of the thermostat, how the cooling system actually cools, and get the exact steps for performing a cooling system flush.

1. Free Automotive Classes
Lesson 6: The Cooling
System
Jeff Crawford
Crawfords Auto Repair
www.CrawfordsAutoService.com

2. Recall Chapter 5

3.  The combustion process and movement of
mechanical parts both create extreme
heat in the engine which must be cooled.
 The cooling system keeps the engine
temperature within operating range.
 (The cooling system is not related to the
AC system)
The Cooling System

4. Source: cdxtextbook.com

5.  Radiator
 Thermostat and Housing
 Water Pump
 Cooling Fan
 Radiator Hoses
 Heater Hoses
 Coolant
Major Components of the Cooling
System

6.  “Ooh, I’m gonna have to go get myself
some coolant!”
Disney/Pixar’s Cars 2

7.  The Thermostat opens with heat, due to
wax element in the thermostat. The more
it opens, the more coolant can pass
through.
 Image source: How Stuff Works
Thermostat

8.  The coolant passes through designated
passages throughout the engine (coolant
does not mix with other fluids)
 Heat transfers to the coolant
 The coolant runs to the radiator where
heat is released into the air.
How the Cooling System Cools

9.  Preventative Maintenance
 Avoid overheating
 Avoid electrolysis (microscopic breakdown
of metals in the engine block)
 May be needed even sooner than
indicated by the manufacturer
 Low coolant level may indicate a leak
Cooling System Maintenance

10. Cooling System Flush

11.  Refer to the owner’s manual for locations
of each part of the cooling system.
 Open the radiator drain to drain the
system, collect the drainage in a
container.
 Remove the thermostat.
 Disconnect the lower radiator hose
 Force coolant through the thermostat
housing, upper hose and engine block
with garden hose until water runs clear.
Steps for Cooling System Flush

12.  Connect the garden hose to the radiator,
flush until the water runs clear.
 Completely drain the cooling system of all
water
 Reinstall the thermostat
 Disconnect the reservoir and flush with
garden hose until water runs clear.
 Completely drain reservoir.
 Connect the hoses and close the drains.
Flush Steps Continued

13.  Perform a pressure test (next slide)
 Fill the cooling system with new coolant to
manufacturer’s specification and distilled
water. Use 50/50 mixture of coolant and
distilled water or pre-mixed coolant
 (Distilled water is necessary so you don’t
have impurities in the cooling system)
Flush Steps Continued

14.  Connect pressure tester where the
radiator cap goes.
 Pump pressure to amount specified on the
radiator cap.
 Leave pressure on for 20-30 min
 Inspect the cooling system for leaks
 Disconnect pressure tester and connect it
to the radiator cap and pump to specified
amount to test the cap
Pressure Test

15. Pressure Testing the Cooling
System

16. Cooling System Pressure Tester

17. The steps to a cooling system
flush and pressure test will all
make more sense with our
video on YouTube.

18. Questions?

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s-auto-repair-guide-free-ebook/
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