1, the water level in the heater tank is too low: if the water level in the heater tank is too low, the vibration during the acceleration of the car will make the water waves bubble, resulting in bubble sound.
2. Failure of the heater water tank pump: Failure of the heater water tank pump will lead to poor water flow and bubble sound.
3. Air leakage in the water pipe of the heater box: If the water pipe of the heater box leaks, bubbles will enter the water pipe, resulting in bubble sound.