Lesson 5/Learning Event 2
FIGURE 71. COOLING FAN.
Usually the fan blades are not all equally spaced around its hub. This is so the noise made by each blade will
not be the same. If all the blades made identical noises, they would add together to make one loud noise. But
by making noises slightly different (different pitch), they do not add together; therefore, the fan sounds quieter.
If the fan is set very far from the radiator, some air is drawn into the fan from its sides without going through
the radiator core. This reduces the amount of air flowing through the core and the amount of engine cooling.
Some vehicles have a funnel-shaped part known as a shroud to prevent the air from bypassing the radiator.
The larger end of the shroud is generally bolted to the radiator frame with the smaller end extending out to
enclose the fan.
Thermostat
The coolant jacket, radiator, coolant pump, and fan work together to remove unwanted heat from the engine.
But the system, as studied so far, would cool the same amount all the time. The cooling system must be able
to vary the amount of cooling it does to reduce the amount of warm-up time and to regulate engine
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