Starting the Brake Master Cylinder overhaul includes both reservoir cap removal and brake fluid drainage from the reservoir. Start by disconnecting the reservoir and grommets from the body of the master cylinder before placing the mounting flange in a vise clamp. First remove the snap ring followed by the primary
Piston assembly and finally the seal. Carefully pull out the secondary Piston by directing a low air stream to the bore opening that is positioned 25 mm (1 inch) from a padded surface to catch the Piston avoiding all direct contact with people. Plug the rear port then apply pressure to the front port with air to remove the seals followed by removal of the spring retainer and spring. After cleaning metal components with denatured alcohol while cleaning rubber parts with brake fluid test the diaphragm function while inspecting the master cylinder bore for signs of corrosion especially when corrosion is detected the master cylinder requires replacement. Add clean dot 3 motor vehicle brake fluid as a lubricant for all parts which includes grommets, seals, and cylinder bore and select new seals for assembly. Begin by installing the secondary Piston spring and retainer before placing the primary seal and secondary seal to the secondary Piston, which needs to be inserted into the master cylinder body. Place the primary Piston assembly along with its installed seal into the master cylinder body while placing the snap ring and compressing the primary Piston to set it in place. Place two new grommets before you install the reservoir on the master cylinder body and the reservoir cap.