Warning: Disc brake pads must be changed on both rear wheels at the same time. Never change pads on only one wheel as this can cause uneven braking. The dust generated by the wear of the pads may contain asbestos, which is a health hazard. Never blow it off with compressed air or inhale any of this dust. Do not use gasoline-based solvents to clean brake parts. Use only brake cleaner or ethyl alcohol.
1. Where it is installed, remove the pad wear sensor connectors from the caliper body, remembering how the wires are routed.
2. Using a hammer and a suitable drift, carefully knock out the fingers and remove the hold-down springs (see fig. 5.2, a, b).
Pic. 5.2, a. Knock out your fingers on the rear brake...
Pic. 5.2, b... and remove the clamping springs
3. Remove the pads from the caliper body, remembering the correct location of the wear sensors. If necessary, remove the shims that are installed between the pads and pistons (see fig. 5.3, a, b).
Pic. 5.3, a. Remove the inner pad...
Pic. 5.3b. and the outer pad from the caliper
4. Check the condition of the pads, as indicated in paragraph 4. Replace the clamping springs, pins and washers (if provided), if pads need to be replaced.
5. Brush off dust and dirt from the caliper and cylinder, but do not inhale them as this is hazardous to health. Check the cylinder dust covers for damage and for visible signs of fluid leakage, corrosion or damage. If found, the caliper should be repaired - see paragraph 8.
6. When installing new pads, it is necessary to drown the piston of the cylinder to make room for the pads. Use either a vise. or a wooden object to press the piston like a lever. If the liquid level in the reserve tank exceeds the mark "MAX', remove some of the fluid from the master cylinder reservoir to prevent overflow when you push the piston in. You can use a syringe or a brake bleeding procedure (see paragraph 2).
Warning: Do not try to suck up the liquid by mouth as it is very poisonous; use the syringe.
7. If the pads on the back have damping pads that connect to the caliper pistons, do not apply any lubricant to the back of the pads. If the back of the pads is flat, apply brake grease to the ends of the pad plate (Mercedes-Benz recommends using brake paste part number 0019891051); do not apply a lot of paste so that it does not get on the friction linings (see fig. 5.7, a, b).
Pic. 5.7. V. If damping pads are located on the reverse side of the pads (b) do not apply any lubricant to the pad
Pic. 5.7b. If the back surfaces of the pads do not have pads, apply grease to the ends of the pad plate (shown by arrows)
8. Make sure that the wear sensors are securely installed in the plates of each pad and (where they are installed) install shims on the back of each shoe.
9. Install pads and (where provided) washers in place in the caliper so that the friction linings are facing the brake disc.
10. Install new pressure springs on top of the pads.
11. Install the fingers so that they pass on top of the spring and hammer them all the way into the caliper body.
12. Make sure the wires are routed correctly and connect them to the wear sensor pads on the caliper.
13. Press the brake pedal several times so that the pads are pressed against the brake disc and normal pedal pressure is restored.
14. Repeat the steps on the remaining caliper.
15. Install the wheels, then lower the vehicle to the ground and tighten the wheel bolts to specification.
16. Check fluid level as described in section "Weekly check". Thoroughly check the operation of the brakes before leaving on the road.
Warning: New pads will not brake effectively until they are worn in to the discs. Avoid hard braking as much as possible for the first few hundred kilometers.