What are the symptoms of automobile thermostat failure? Will the water temperature be high if the thermostat fails?

The automobile thermostat automatically adjusts the amount of water entering the radiator according to the temperature of cooling water, changes the circulation range of water to adjust the cooling capacity of the cooling system, and ensures that the engine works in a suitable range. That is to say, the thermostat is broken, which may cause the engine water temperature to increase or decrease abnormally. If the thermostat of the car is broken, the most obvious symptoms will be displayed on the water thermometer. If the main valve of the thermostat is opened too late, the engine will overheat. If the engine is started too early, the engine warm-up time will be prolonged and the engine temperature will be too low, thus affecting the efficiency.