2. Secondly, the water pump impeller is damaged or lost, which makes the flow through the warm air small water tank insufficient and the water temperature too high to clean the water tank. The heater uses the circulating water of the engine to supply heat to the cab through the fan at about 90 degrees. If the engine water temperature is normal but the warm air is not hot, it means that the circulating water has not taken a big cycle. The above is the content that Hitachi 120 excavator is not hot.