Camry 2.4L instrument panel abnormal sound. When the cold car started in the morning, I heard the clear sound of running water from behind the dashboard. What happened?

The problem is that there is not enough cooling water. Standing for another night, the indoor heating cabinet is short of water. After starting the engine, water will flow from the engine to the room, and there will be the sound of running water. Replenish the coolant first, and then check whether there is any leakage. This should be repaired in time, otherwise the high water temperature in summer will damage the vehicle. thank you