Flushing Brake System Completely
WARNING: This page is about a different car, the 2005 BMW 645Ci and 2004 BMW 645Ci. However, it is still accessible from the selected car via links, so may be relevant.
Connect bleeder hose with collecting tray to bleeder valve on rear right brake caliper.
Open bleeder valve and purge until clear, bubble-free brake fluid emerges.
Close bleed valve.
Follow same procedure on rear left, front right and front left wheel brake.