NOISES FROM THE FUEL TANK AT IDLE: All vehicles except the F48 (X1): While driving slowly with low RPM or while idling a faint knocking or fluttering noise can be heard from inside the fuel tank with a low fuel level (approximately less than 2 gallons). The customer may describe this noise as a "helicopter noise" from the rear of the vehicle. F48 (X1) only: While driving slowly with low RPM or while idling a faint knocking or fluttering noise can be heard from inside the fuel tank when the tank is full. The customer may describe this noise as a "helicopter noise" from the rear of the vehicle. CAUSE Pressure fluctuations from the tank ventilation valve will cause the fuel tank filler pipe non-return valve to vibrate. In some cases, the vibration can be heard inside the vehicle.
