Thermostat: Description and Operation

DESCRIPTION
A pellet type thermostat is used in the coolant outlet passage to control the flow of engine coolant, to provide fast engine warm up and to regulate coolant temperatures.

OPERATION
A pellet element in the thermostat expands when heated and contracts when cooled. The pellet element is connected through a piston to a valve. When the pellet element is heated, pressure is exerted against a rubber diaphragm which forces the valve to open. As the pellet element is cooled, the contraction allows a spring to close the valve. The valve remains closed while the coolant is cold, preventing circulation of coolant through the radiator. At this point, coolant is allowed to circulate only throughout the engine to warm it quickly. As the engine warms, the pellet element expands and the thermostat valve opens, permitting coolant to flow through the radiator, where heat is dissipated through the radiator tube walls. This opening and closing of the thermostat permits enough coolant to enter the radiator to keep the engine within operating limits.