310T Engine And Supporting Systems Practice Exam

The thermostat acts as a temperature-sensitive valve that controls coolant flow to keep the engine near its optimum operating temperature by opening and closing at a set temperature. When the engine is cold, it stays closed to keep heat in and help the engine warm up quickly. Once the coolant reaches its set temperature, a wax-filled element expands and opens the valve, allowing coolant to circulate to the radiator to be cooled. This cycling maintains the engine in a narrow temperature range, which helps fuel efficiency, emissions, and performance. Typical opening temperatures are around 180–195°F (82–90°C), though this can vary by vehicle. It doesn’t filter impurities, which is the role of a coolant filter or maintenance items; it does not pump coolant—that is done by the water pump; and it does not seal the radiator cap.