Place a wooden panel underneath to avoid damaging the piston. Remove the lip seal. Use wedge "3409" for this.
When removing, do not damage the cylinder surface.
Installation
Clean the piston surfaces and the lip seal only with alcohol and then dry. Before installation, apply a thin layer of mounting paste "G 052150 A2" to the piston and sealing ring. Insert the inner sealing ring into the groove "arrow" of the brake caliper.
Press the protective cap onto the brake caliper body so that it fits snugly against the brake caliper body on all sides. After this, do not remove the protective cap from the brake caliper body by hand.
Before installation, apply a thin layer of mounting paste "G 052 150 A2" to the piston and sealing ring. Lightly press the brake piston against the protective cap. To avoid damaging the sealing cuff, do not tilt the piston. Blow out the protective cap with compressed air (no more than 3 bar). The outer edge of the sealing cuff will be above the piston. Using the piston pressing tool "T10145", press the brake piston into the brake caliper.
To avoid damaging the sealing cuff, do not tilt the piston. In this case, the inner working edge of the protective cap is installed in the groove in the piston.
(The original article is posted on the resource: AUDImanual)