The function of the thermostat is to automatically adjust the amount of water entering the radiator according to the temperature of the cooling water, so as to ensure that the engine works within the appropriate temperature range and can save energy. The thermostat must be kept in good working state, otherwise it will seriously affect the normal operation of the engine. If the thermostat is opened (here refers to the thermostat main valve) too late or cannot be opened, it will cause engine overheating; Start too early, the engine preheating time is prolonged, the engine temperature is too low.