(Engine Operating Conditions)Operation

How is coolant circulated?

Through the engine by a belt or timing chain driven water pump

Why does the engine crankshaft drive the belt?

So the water pump actually uses engine power to operate

The water pump takes coolant in and:

pushes it into the engine block

What does the the coolant do after being pushed into the engine block?

It makes its way upward into the cylinder head, and then returns to the inlet of the water pump through the bypass tube

As long as the thermostat is closed(engine below operating temperature):

The coolant will continue to circulate in this manner

When the thermostat opens:

Hot coolant moves past the thermostat into the upper radiator hose, and then the coolant enters the radiator itself

One of the methods used to raise the boiling point of the water has already been mentioned:

using coolants made up of a 50/50 mix of ethylene glycol and water

The other method that can be utilized is:

Raising the pressure in the cooling system which the radiator cap is responsible for

Most radiator caps are designed to:

Maintain anywhere from 9 to 16 pounds per square inch(psi) of pressure in the cooling system

For every 1 psi of pressure that is placed on the cooling system:

The boiling point of the coolant is raised approximately 3 degrees Fahrenheit

A 15 psi radiator cap would then raise:

The boiling point of the coolant to between 212 degrees F and 260 degrees F

Radiator caps incorporate two separate valves:

A pressure valve and vacuum valve

As the engine warms up:

The coolant in the cooling system will tend to expand

This expansion will raise the pressure in the cooling system but when the pressure reaches the radiator cap’s rating:

The pressure valve in the radiator cap will lift and allow some coolant to flow from the radiator into the coolant recovery bottle

This flow will continue as:

The cooling system pressure exceeds the rating of the radiator cap

The cooling level in the recovery bottle:

will rise until the engine reaches operating temperature

When the engine is shut down and begins to cool:

The coolant will contract and create a low pressure area inside the cooling system

If left unchecked, this low pressure area would:

Cause the radiator hoses to collapse and have an adverse effect on the cooling system at engine startup