This engine thermostat controls coolant flow to maintain the engine's operating temperature within its designed range. It sits in the coolant circuit between the engine block and the radiator, opening when the coolant reaches a specified temperature to allow circulation through the radiator and closing when the engine is cold to speed warm-up. A failed thermostat that sticks open prevents the engine from reaching normal operating temperature, reducing efficiency and increasing wear. A thermostat that sticks closed causes overheating and potential gasket or head damage. The original manufacturer's calibration matches the spring rate and wax-pellet expansion curve that the engine's cooling system was designed around, ensuring the opening temperature and flow rate are correct for the host tractor.