Caution: Brake fluid may irritate eyes and skin. In case of contact, take the following actions:

Caution: Use only Delco Supreme 11, GM P/N 12377967 (Canadian P/N 992667), or equivalent DOT 3 brake fluid from a clean, sealed container. Do not use fluid from an open container that may be contaminated with water. Improper or contaminated fluid could result in damage to components, or loss of braking, with possible injury.

Notice: When filling the master cylinder, use only Delco Supreme 11, GM P/N 12377967 (Canadian P/N 992667), or equivalent DOT 3 brake fluid. Do not use a container which has been used for petroleum based fluids, or a container which is wet with water. Petroleum based fluids will cause swelling and distortion of rubber parts in the hydraulic brake system, and water will mix with brake fluid, lowering the boiling point. Keep all fluid containers capped to prevent contamination.

Notice: Do not hone the master cylinder bore. When the brake master cylinder is overhauled, it is recommended that the cylinder body be replaced rather than CLEANED UP by honing the bore. The master cylinder has a hard, highly polished BEARINGIZED surface, which is produced by diamond boring followed by ball or roller burnishing under heavy pressure. Honing will destroy this hard smooth surface and cause rapid wear of the rubber cups.

Notice: Do not clamp on the master cylinder body. Doing so may damage the master cylinder.

1. Remove the reservoir (2) from the master cylinder (4). Refer to Master Cylinder Reservoir Replacement .
2. Remove the master cylinder from the booster. Refer to Master Cylinder Replacement .



3. Remove the piston stopper snap ring (1) from the master cylinder (2).
4. Remove the piston stopper.
5. Remove the cylinder cup.
6. Remove the plate.
7. Pull the primary piston assembly carefully from the master cylinder in order to prevent damage to the inside of the cylinder wall.



8. Remove the secondary piston assembly carefully from the master cylinder (1) by tapping the flange on a piece of wood (2) or two soft objects.
9. Remove the secondary piston pressure cup.
10. Remove the piston cup.
11. Remove the O-ring.
12. Inspect all disassembled parts for wear or damage. For a view of the disassembled master cylinder, refer to Master Cylinder Description . Replace parts if necessary.

Important: DO NOT reuse piston cups.

13. Wash disassembled parts with brake fluid.
14. Inspect the master cylinder bore for scoring or corrosion (pits or excessive roughness). Replace a corroded master cylinder.

Important: Do NOT use a cloth in order to dry the cylinder, because lint from a cloth will stick to the cylinder bore surfaces.

15. Rinse the cylinder in clean brake fluid. Shake excess rinsing fluid from the cylinder.

1. Install the O-ring to the master cylinder (2).
2. Install the following to the master cylinder:

•	The new piston cup

•	The secondary piston assembly

•	The new secondary piston pressure cup

3. Install the primary piston assembly to the master cylinder.
4. Install the plate.
5. Install the cylinder cup.
6. Install the piston stopper.



7. Depress and install the piston stopper snap ring into the master cylinder (2).
8. Install the master cylinder to the brake booster. Refer to Master Cylinder Replacement .



9. Apply a thin coat of brake fluid around the new grommets (3), and install the grommets to the master cylinder (4).
10. Install the reservoir. Refer to Master Cylinder Reservoir Replacement .