WD Catalog 2018

Heater Components

and Controls

• Engine Coolant or Anti-freeze

• Cooling System Thermostat and Radiator Pressure Cap

• Water Pump

• Heater Components and Controls

• Chapter Review

Engine Coolant or Anti-freeze

Ethylene glycol-type coolant (anti-freeze) is mixed with water and used in most

vehicle cooling systems today. Additives in the coolant formula lubricate the

water pump, reduce the chance of rust or corrosion, and prevent foaming.

Although it is often called permanent anti-freeze, the additives break down in

time and loose their protective qualities. For this reason coolant should be

changed at regular intervals. Five main reasons to use coolant in the engine

are:

It has a much lower freezing point than water.

It has a higher boiling point than water.

It is inexpensive.

It prevents corrosion for a reasonable period of time.

It absorbs and gives off heat energy effectively under a great

range of operating conditions.

Mixing 60% ethylene glycol with 40% water protects the cooling system from

freezing to -65 degrees Fahrenheit. Adding more anti-freeze does not prevent

freeze up at lower temperatures, but it does raise the boiling point of the

solution.

WARNING

Use care in handling anti-freeze. It is a petroleum based

liquid that can irritate the skin and eyes. The sweet

taste is appealing to animals and can be deadly if con-

sumed. Check for local regulations on disposal and recy-

cling.

Cooling System Thermostat and Radiator Pressure Cap

These two cooling system control devices affect heater system operation, in-

cluding coolant temperature, circulation, boiling point, and coolant overflow

and recovery system. Figures 3-1 and 3-2 illustrate the function of the thermo-

stat and radiator pressure cap respectively. Descriptions of how the thermostat

and radiator cap work follow the figures.

Chapter

3-1

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