Mercedes e200 water temperature is unstable. The computer checked the throttle. Is the water temperature sensor changing or unstable? Occasionally 70 80 90 degrees?

Is the water temperature unstable? Or will the temperature soon become high and stable from 70-80-90? That is, after the temperature rises, it will not fall again. First, if you are talking about ups and downs, I suggest you consider the following aspects. This throttle doesn't matter. 1. There is scale on the contact surface between the water temperature sensor and the coolant; 2, thermistor aging; 3. The voltage regulator is not working properly; 4, water thermometer heating coil short circuit; The hands of the watch grazed the surface. Second, if you're talking about going high. The temperature can't drop. Then I suggest you solve it from the following aspects. 1. The thermostat is broken. Coolant only circulates in a small range and does not dissipate heat through the water tank. 2. The cooling fan does not rotate. The temperature control switch may not be turned on, or the water temperature sensor may be faulty. 3. The water pump is out of order. The belt is broken due to slipping or sticking of the impeller. 4. Insufficient cooling medium. Insufficient coolant or leaking water tank.