Fully rinse the brake system
WARNING: This page is about a different car, the 2013 BMW X5 M, 2012 BMW X5 M, 2011 BMW X5 M, and 2010 BMW X5 M. However, it is still accessible from the selected car via links, so may be relevant.
Connect vent hose with collecting vessel to vent valve on rear right brake caliper.
Open vent valve and purge until clear, bubble-free brake fluid emerges.
Close vent valve.
Follow same procedure on rear left, front right and front left wheel brake.