Brake Booster Vacuum Hose
WARNING: This page does not describe the selected car, but rather 7 other vehicles, including the 2006 BMW X5, 2005 BMW X5, 2004 BMW X5, 2003 BMW X5, and 2002 BMW X5. However, it is still accessible from the selected car via links, so may be relevant.
Operation is identical to replacing non-return valve with the addition of removing vacuum hose on suction jet pump. See BRAKE BOOSTER NON-RETURN VALVE .