Brake Caliper: Reassembly
WARNING: This page is about a different car, the 1994 BMW 525iT. However, it is still accessible from the selected car via links, so may be relevant.
Coat piston and caliper bore with brake assembly lubricant. Install piston seal. Install dust boot on piston. Using wooden block, install piston and dust boot. Ensure piston is not tilted when installing.