You need to remove the caliper, catch the piston, remove the piston from the caliper, the piston seal from the caliper and the bleeder valve and cap, clean the caliper slide bushing, the caliper set ring, the piston, caliper carrier, and caliper housing in clean brake fluid, dry the parts with non-lubricated, compressed air, blow out all of the passages in the caliper housing and bleeder valve, inspect the piston for scoring, corrosion, and any damage to the chrome plating, and inspect the caliper bore.