Thermostat: Description and Operation

ENGINE THERMOSTAT
The engine cooling thermostats are wax pellet driven, reverse poppet (3.2/3.5L), and dual poppet (2.7L) types. The thermostats are located in the inlet side of the engine to provide fast warm up and to optimize a constant temperature in the engine. The thermostats are designed to prevent leakage through them and to guarantee a minimum engine operating temperature of 82°C (180°F). They also automatically reach wide open at a temperature of approximately 102°C (215°F) so they do not restrict flow to the radiator as temperature of the coolant rises in hot weather to around 104°C (220°F). Above 102°C (215°F) the coolant temperature is controlled by the radiator, fan, and ambient temperature, not the thermostat.