2. Pull the piston out of the caliper. Do not grab it with pliers - you will scratch the metal. Follow the following procedure:
- a. Place a narrow piece of wood or some rags against the piston but inside the caliper grip.
- b. Inject a certain amount of compressed air - no more than 200 kPa - into the brake pipe duct. Watch out for your fingers: let the piston squeeze out the wooden stopper.
3. Remove the piston, boot and seal.
4. Clean the piston and channel with clean brake fluid. Examine the surfaces very carefully; they must be absolutely smooth. Any scratch or rust is grounds for replacement. Very light surface rust can be removed with very fine abrasive paper soaked in brake fluid, but any pitting should be replaced.
For installation:
5. Apply brake cylinder lubricant to the new piston seal and install the seal in the cylinder groove.
6. Put the cover on the piston.
7. Lubricate the caliper bore and piston with clean brake fluid. Install the piston in the channel, first with the solid end. This is a laborious operation due to the very high precision required; keep the piston straight in the bore. Be patient.
8. Make sure the piston boot is on the edges around the caliper bore. Push the piston all the way, and then the caliper will easily be installed on the brake pads.
9. Install the caliper. Fill the reservoir as needed and bleed the brake system.