Master Cylinder

Disassembly

1. Clean the outside of the master cylinder thoroughly. Remove the cap. Drain all brake fluid from cylinder. Always discard used brake fluid.

   NOTE: If master cylinder is to be put into vise to aid in disassembly, mount into vise by flange only to avoid damage to bore or reservoir areas.

2. Depress the primary piston, and remove snap ring from retaining groove at the open end of the bore.
   
   
   
   

3. Remove primary and secondary piston assemblies from master cylinder. Tap open end of cylinder on bench to remove pistons. If secondary piston does not readily come out, apply air pressure to secondary outlet port to assist removal.

4. Remove fluid control valve as outlined.
   
   
   
   

Inspection

1. Wash master cylinder body, especially bore, along with primary and secondary piston assemblies in clean brake fluid. Denatured or isopropyl alcohol can be used instead.

    CAUTION: Blistering or swelling indicates contamination of brake fluid by a petroleum-based solvent or oil. In that case, all rubber components in the brake hydraulic system must be inspected and replaced and the entire system must be flushed with clean brake fluid to prevent recontamination. Replace the following components:

   • Fluid control valve
   • Front brake caliper seals
   • Rubber front brake hoses
   • Rear wheel cylinder seals
   • Rubber rear brake hoses
   • Pressure control valves
   • Primary and secondary piston assemblies
   • Reservoir grommets
   • Cap assemblies

2. Inspect seals on primary and secondary piston assemblies for cuts, nicks, scratches, or signs of wear and for presence of any blistering or swelling.

   NOTE: The aluminum body of the master cylinder is anodized. Some signs of bore wear on the anodized surface, as evidenced by lighter areas of the anodized surface, are normal and not detrimental.

    CAUTION: Honing of the bore on aluminum master cylinders is not permitted as the anodic coating and hardness could be removed.

3. Inspect master cylinder bore for pitting, corrosion, or heavy wear. Heavy wear is characterized by scoring or galling of metal.

Assembly

1. Dip replacement piston assemblies in clean Heavy-Duty Brake Fluid C6AZ-19542-AA (ESA-M6C25-A) or DOT-3 equivalent, for lubrication prior to assembly into cylinder.

2. Install secondary (smaller) piston assembly into bore, spring end first.

3. Install primary piston assembly, spring end first.

4. Depress primary piston, and install snap ring.

5. Fill and bleed master cylinder, and install plugs into outlet ports. Refer to Pressure Brake Bleeding procedure.

6. Install cap on master cylinder reservoir, and secure.