Engine Cooling: Operation: Thermostat

The thermostat allows rapid engine warm-up by preventing engine coolant flow through the radiator and by limiting engine coolant flow through the cylinder block when the engine is cold. During warm-up and at engines speeds above approximately 1, 800 Revolutions Per Minute (RPM), a bypass valve opens to control the coolant flow and pressure. The bypass valve opens to protect the engine components. When the thermostat opening reaches 6 mm (0.24 in.), the by-pass flow is shut-off. When the thermostat opening exceeds 6 mm (0.24 in.), the radiator engine coolant flow is further controlled up to the point where the thermostat is fully open. At this point maximum radiator engine coolant flow is achieved to provide maximum cooling.