1. All four pads on one axle should be replaced to ensure uniform braking performance.
2. The wear and condition of the brake discs should be checked. They should not have any scratches or deep grooves (see "Replacing brake discs").
3. It is necessary to check the condition of the protective boot, as well as how freely the piston moves in the brake cylinder.
4. When the brake pads are removed, do not press the brake pedal under any circumstances, otherwise the brake cylinder pistons will come out of their holes.
Sequence of works
1. Place the car on supports and secure it. Remove the front wheel.
2. Use your hand to pull the caliper bracket outward, to do this, press the brake piston slightly into the hole.
3. Use a screwdriver to pry off the plastic cover of the brake pad wear sensor connector. Remove the cover and pull out the connector.
4. Use a screwdriver to pry the retaining clip away from the caliper.
5. Use a screwdriver to remove the protective caps from the guide pins.
Fig. 8.13. Using an Allen key to loosen and remove the guide pins from the supports
6. Unscrew the guide pins (Fig. 8.13) from the upper and lower supports of the caliper, holding the hexagonal slot near the rubber boot with an open-end wrench.
7. Remove the caliper and hang it on a wire so that the brake hose does not stretch out.
Fig. 8.14. The inner shoe is mounted on the caliper piston (arrow) via a return spring. Thus, when the brake pedal is released, the brake disc again gets free play
Fig. 8.15. Replacing the front brake pads: 1 – caliper bracket (removed and hung on a wire); 2 – outer brake shoe; 3 – inner brake shoe (the brake pads are removed from the bracket, a wear sensor is installed on the inner pad)
8. Remove the inner shoe from the brake piston (Fig. 8.14). It is secured with a retaining clip (Fig. 8.15).
9. Remove the wear sensor from the inner pad.
10. Remove the outer shoe from the bracket.
Fig. 8.16. After long-term use, the caliper parts and pad guides become covered with brake dust. To ensure proper operation, clean the bracket and caliper with a wire brush before installing new pads
11. Before assembly, clean the caliper parts with a soft metal bristle brush (Fig. 8.16) or a cloth soaked in alcohol. Do not use mineral solvents or tools with sharp edges. Brake dust deposits and corrosion on the caliper parts can lead to uneven wear of the pads.
12. Check the condition of the brake piston mud boot. If any damage is found, replace it, as dirt penetration will quickly cause the piston to seize.
Fig. 8.17. Pressing the brake piston into the cylinder using a clamp. To protect the piston from damage, it is necessary to place wooden blocks. You can also use an old shoe
(Information copied from the website MercedesMan.ru)
13. Press the piston into the cylinder (Fig. 8.17). Use a wooden mallet or a special clamp to do this. Be careful not to damage the piston surface or the mudguard.
14. When the piston is pressed, the brake fluid from the cylinder will be forced into the reservoir. If necessary, pump out excess fluid.
15. Install the brake pads.
16. Install the wear sensor.
17. Install the caliper and tighten the new self-locking guide pins to a torque of 35 Nm.
18. Place the protective covers on the guide pins.
19. Connect the sensor connector. Pay attention to the wire routing and close the connector protective cover.
20. Install the caliper retaining bracket. After installing the bracket in both holes, secure it by pressing it under the caliper bracket. If installed incorrectly, the brake pedal travel will increase.
21. Install the front wheel, lower the vehicle and tighten the wheel mounting bolts to 110 Nm.
22. Replace the brake pads on the other side of the car.
23. With the vehicle stationary, press the brake pedal several times to ensure that the pads are in the correct position.
24. Check the brake fluid level.