First, remove the brake-calliper out of the lorry in such a way that your fingers won't stay in front of the caliper piston(s) while using compressed air since the caliper piston(s) can be readily thrust out which is a major injury confirmation factor. Use clean cloths for padding the interior of the caliper housing while undertaking piston removal, use only a little low-pressure compressed air through the fluid inlet hole to facilitate the ease of pistons sliding out of the bores. Pull off the retaining ring that holds the dust boot into the caliper housing and remove the piston dust boot seal from the seal counterbore in the caliper and throw it away. For the removal of the piston seal from the caliper bore, use a small wooden or plastic tool to take it out and throw it away. Next, take off the bleeder valve cap and blew deer valve. Do not use abrasives to clean out the Brake Caliper Piston and check the caliper bore for cracks, scoring, pitting, high rust, or corrosion. Clean or degrease the caliper piston bore, seal counterbore, and caliper piston using denatured alcohol or its equivalent, and blow with clean, non-lubricated, filtered compressed air. If a light rust or corrosion has occurred try to pick it off with fine emery paper; if not changeable change the caliper assembly. Replace the caliper assembly if there are any cracks, scoring, pitting, excessive rust, or corrosion that is observed in the caliper bore, and inspect the caliper piston for similar damage and replacement if needed. For assembly, you may lubricate the new piston seal with brake fluid saturn p/n 21013073 or equivalent brake fluid of the dot-3 type from a new, sealed container, and use it to install in the caliper bore. Apply small amount (thin layer) of saturn p/n 21013073 or equivalent dot-3 brake fluid onto exterior side of caliper piston before installing bottom half of the caliper piston into caliper bore. The new piston dust boot seal should be placed over the caliper piston and compress the caliper piston into the bottom of the caliper bore while properly seating the piston dust boot seal into the contrabore. Mount the retaining ring that holds the dust boot to the caliper housing then mount the bleeder valve to the caliper with 11nm (97 in lbs) torque and then mount the bleeder valve cap. Finally, you should install the brake caliper back on the vehicle.