PRIN. OF INTERNAL COMBUSTION ENGINES - OD1619 LESSON 2/TASK 3
(3) Variable Pitch (Flexible) Fan Blades (figure 69). Some vehicles are equipped
with blades that are made of flexible aluminum or fiberglass. These fan blades are
made to change pitch as the speed of the fan increases so that the fan will not
create excessive noise or draw excessive engine power at highway speeds.
FIGURE 69. VARIABLE PITCH FAN.
(1) Purpose. The water pump starts the coolant circulating through the system as
the engine is started, no matter how low the temperature. Therefore, it is
necessary to install a thermostat to ensure quick warmup and prevent overcooling in
cold weather. A thermostat regulates engine temperature by automatically
controlling the amount of coolant flowing from the engine block to the radiator
(2) Operation. The thermostat is merely a heatoperated unit that controls a
valve between the engine block and the radiator. It is usually located in series
with the engine coolant outlet in a casing called the thermostat housing. The
thermostat, by design, is made that if it fails, it will be in the opened position
allowing the free circulation of coolant through the engine.