Master cylinder — removal, overhaul and installation (Peugeot 305)

1. A sign of internal brake fluid leaks behind the master cylinder seals is a slow sinking of the brake pedal when you press it with your foot, if inspection shows that there are no external leaks in the system. Internal leaks can be caused by wear of the seals themselves or the master cylinder, as well as the presence of grooves on the cylinder walls. In any case, it is necessary to remove and overhaul the master cylinder. The master cylinder is bolted to the front surface of the brake booster and the brake reservoir is mounted on top of it (see photo). Before overhauling the master cylinder, you need to purchase a special repair kit for it.


2. Remember that brake fluid corrodes paint. Before loosening the master cylinder fittings, place a plastic sheet and rags underneath it.



3. Remove the brake reservoir cap and remove all the fluid from it using an old syringe. The removed liquid cannot be reused.

4. Disconnect the brake lines from the master cylinder and carefully move them to the side so that they do not interfere, plug the open ends of the lines to prevent dirt from getting into the system.

5. Remove the 2 nuts with spring washers securing the master cylinder to the servo booster, wrap the cylinder in rags and remove it. Remove the reservoir from the master cylinder. The two rubber bushings on which it was installed must be replaced with new ones during assembly.

6. When disassembling the master cylinder, carefully note the position of its various parts so that you can later install them in their original order. Press on the piston, which is visible in the cylinder bore, and remove the piston stop. While still pressing on the piston, remove the retaining ring from the end of the cylinder and pull out the pistons. If necessary, the pistons can be blown out with compressed air, but wrap the cylinder with a rag to prevent the pistons from flying in all directions.

7. Clean all metal parts with methyl alcohol (do not use abrasive materials or scrapers).

8. Select new seals from the kit that exactly match the old ones and soak them in clean brake fluid before installation.

9. Carefully inspect all metal parts for wear, corrosion and obvious damage. Scratches and abrasion marks on the inner surface of the master cylinder (even the most insignificant ones) require its replacement (best when collected).



10. The master cylinder is assembled in reverse order. Absolute cleanliness must be maintained when working. Wipe all cylinder parts dry with a clean, lint-free cloth and lubricate them thoroughly with clean brake fluid before assembly. After completing the assembly, wipe the cylinder dry and only then install new rubber bushings and the brake reservoir.

11. Installation of the master cylinder is carried out in reverse order. Connect the brake lines to the cylinder, fill the reservoir with fresh brake fluid and bleed the system (see section 3).

12. Take a test drive to check the operation of the brakes.