Previa Van 2WD L4-148.8 2438cc 2.4L DOHC (2TZ-FE) (1992)
Thermostat: Description and Operation
THERMOSTAT
The thermostat has a wax bypass valve and is mounted in the water inlet housing. The thermostat is a type of automatic valve operated by
fluctuations in the coolant temperature. This valve closes when the coolant temperature drops, preventing the circulation of coolant through the
radiator, thus permitting the engine to warm up rapidly. Because the bypass valve is open, the coolant already inside the engine continues to
circulate through the engine.
When the coolant temperature has risen, the valve opens and the bypass valve closes, allowing the circulation of coolant through the radiator. The
WAX inside the thermostat expands when heated and contracts when cooled. Heating the wax thus generates pressure which overpowers the force
of the spring which keeps the valve closed, thus opening the valve. When the wax cools, its contraction causes the force of the spring to take effect
once more, closing the valve. The thermostat in this engine operates at a temperature of 82 degrees C. (18 F).