Brake master cylinder (Peugeot J5)

Depending on the engine type, master brake cylinders with different bore diameters are installed.

13.4.1. Removal and installation

Removing and installing the brake master cylinder is not difficult. Disconnect the battery before removing. The brake master cylinder is installed in the front part of the brake booster.

• Disconnect the two brake fluid level warning device connectors.
• Unscrew the union nuts of the brake pipes and carefully move the pipes to the side. The master brake cylinder is shown in Figure 182. It looks different on different models. To access the connection points, it is better to remove the spare wheel mount.

• Remove the two nuts from the brake master cylinder on the front side of the brake booster.
• Carefully remove the brake master cylinder. To prevent brake fluid from spilling onto painted surfaces, hold a rag under the cylinder or remove the cylinder at an angle as shown in Figure 183.

• Installation of the master brake cylinder is carried out in reverse order. Tighten the fastener to a tightening torque of 20 Nm.
• Fill the reservoir with fresh brake fluid and bleed the brake system as described in section 13.6. Then bring the brake fluid level in the reservoir to the normal level.

13.4.2. Repair of the master brake cylinder

It is better not to repair the master brake cylinder. If damaged, it is better to install a new cylinder. When purchasing a master cylinder, please specify the vehicle model, as the cylinders are not the same on all models. However, if you have a repair kit, repairing the master brake cylinder is not difficult. In this case, maintaining cleanliness is especially important. The removed cylinder is shown in Figure 184 and can be disassembled as follows:

• Remove the dual-chamber brake fluid reservoir (1). It is secured to fittings in rubber caps (2) and should be pulled upward and wiggled when removed. Pull back both rubber tips (2) with a screwdriver.
• Remove the rubber gasket (3).
• Remove the retaining spacer ring (4) from the cylinder bore. At the same time, lightly press on the push rod to reduce the pressure on the ring.
• Slowly release the push rod and pull the piston with the return spring out of the cylinder. These details are shown in Figure 185.

• Unscrew the stop screw from the side of the cylinder. It holds the intermediate piston inside the cylinder. To avoid damaging the piston when unscrewing the screw, press the piston inward with a wooden stick to reduce the pressure on the piston. Remove the piston and the second return spring from the cylinder. To do this, hit the cylinder on a wooden stand or blow out the parts with compressed air.
• Remove the washer (1), piston seal (2), spacer washer (3), seal (4) and guide pin (5) of the gasket from the piston in sequence.
• Remove the washer and sealing cuff from the intermediate piston.
• If further disassembly of the pistons is required, the overpressure valve, O-ring and brass washer can be removed from it.
• Clean and inspect all parts thoroughly. The cylinder bore should be especially checked. A cylinder with a scratched or corroded working surface must be replaced. Check the patency of all cylinder openings.
• Before assembly, lubricate all parts with brake fluid.
• If the overpressure valve was removed, apply a brass washer, install a sealing ring and secure the valve.
• Place the sealing ring and washer on the intermediate piston.

Assemble the working piston using Figure 186. Sequentially install the guide pin (5), the cuff (4), the spacer washer (3), slide on the seal (2) and press everything together with the washer (1). The piston cuffs have sealing lips, which should be positioned as follows:

* the cuff in front of the piston must face the back of the cylinder,
* The cuff behind the piston must face the front side of the cylinder.

• Carefully insert the intermediate piston and spring into the hole. The piston has a groove into which the thrust screw fits. To align the screw neck and the groove on the piston, push the piston inward with a wooden stick while tightening the screw. When you feel that the piston no longer wants to return under its own pressure, tighten the screw completely.
• Carefully insert the spring and working piston and use the pusher to push the piston inward. Insert the retaining ring into the cylinder groove. Check that the ring is securely seated.
• Finally, install the rubber tips, tank and retaining ring.