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The secret of the thermoatat lies in the small cylinder located on the engine-side of the device.The cylinder is filled with a wax that begins to melt at around 180’F(different thermostats open at different tempertures,but 180’F is a common one).A rod connected to the valve presses into this wax.When the wax melts,it expands significantly,pushing the rod out of the cylinder and opening the valve.By letting engine warm up as quickly as possible,the thermostat reduces engine wear,deposits and emissions.
Fan
Like the thermostat,the cooling fan has to be controlled so that it allows the engine to maintain a constant temperture.
Front-wheel drive cars have electric fans because the engine is usually mounted transversely, meaning the output of engine points toward the side of the car.The fans are controlled either with a thermostatic switch or by the engine computer,and they turn on when the temperature of the coolant goes above a set point.They turn back off when the temperature drops below that point.
Rear-wheel drive cars with longitudinal engines usually have engine-diven cooling fans.These fans have a thermostatically controlled viscous clutch.This clutch is positioned at the hub of the fan,in the airflow coming through the radiator. |
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