Thermostat: Description and Operation

DESCRIPTION - 2.0L/2.4L

Fig. 19 Coolant Outlet Connector - 2.0/2.4L:

The thermostat is located on the front of the engine (radiator side) in the thermostat housing/coolant outlet connector. The thermostat has a air bleed vent located in the flange and an O-ring with a locating dimple incorporated on it. There is a relief in the housing for positioning the air bleed.

OPERATION
The engine cooling thermostat is a wax pellet driven, reverse poppet choke type. The thermostat is designed to provide the fastest warm up possible by preventing leakage through it and to guarantee a minimum engine operating temperature of 88 - 93 °C (192 - 199 °F). The thermostat also will automatically reach wide open so it will not restrict flow to the radiator as temperature of the coolant rises in hot weather to around 104 °C (220 °F). Above this temperature the coolant temperature is controlled by the radiator, fan, and ambient temperature, not the thermostat.

The thermostat is operated by a wax filled container (pellet) which is sealed. When heated coolant reaches a predetermined temperature, the wax expands enough to overcome the closing spring and water pump pressure, which forces the valve to open.