Disc brake pads — removal, inspection and installation

This chapter describes the procedure for removing, checking and installing the brake pads of the front disc brakes. Removing the rear brake pads is generally similar.

Features relating to the front or rear wheels are highlighted specifically.

Brake linings are classified as materials that require an operating permit and are listed in the General Operating Permit Register (ABE).

In addition, they are selected by the manufacturer for specific vehicle models. Therefore, it is recommended to use only pads offered by the manufacturer or approved by the Federal Automobile Administration. Such pads have a number assigned to them by the Federal Automobile Administration.

Attention! If the brake pads are to be reinstalled for further use, they must be marked before removal. Switching the pads from the right wheel to the left and vice versa is not allowed. Such a switch may result in uneven braking of the wheels. Only original brake pads or pads recommended by the vehicle manufacturer must be installed. Be sure to change all the brake pads on the front wheels, even if only one of them has reached the wear limit.

Removal

1. Mark the position of the front wheels on the hub with paint. This will allow you to install the balanced wheel in its original position during assembly.

2. Loosen the wheel mounting bolts. The car must stand on its wheels when performing this operation.

3. Place the front of the car on jack stands, unscrew the bolts and remove the front wheels.

Warning! There is a risk of injury when installing the vehicle on jack stands. Therefore, you should first familiarize yourself with the safety measures when jacking up a vehicle.

4. Right front outer brake shoe. Disconnect plug 1 of the brake shoe wear sensor from connector 2. Pull the plug body, not the wire (see illustration).



5. Unscrew the lower bolt 1 of the brake caliper mounting (see illustration).



6. Lift caliper 2 upwards, using a screwdriver as a lever if necessary (see illustration).




7. Secure the caliper with wire to the steering knuckle or trailing arm.

8. Remove the brake pads 3 from the shoe guide (see illustration).



9. Use a screwdriver to pry up the upper and lower pressure springs of the 4 pads and remove them (see illustration 2.8).

Attention! When the brake pads are removed, do not press the brake pedal. Otherwise, the piston will be pushed out of the brake cylinder. If the piston does come out of the cylinder, remove the caliper and deliver it to a specialized workshop for repair.

Examination

10. Clean the brake pad seating and guide surfaces and the brake disc with a suitable soft metal brush and wipe it with a rag soaked in alcohol. Do not use solvents containing mineral oils or tools with sharp edges.

Caution: Use only alcohol to clean the brake mechanism.

11. Before installing the pads, check the brake disc for ribbing by running your hand over it. Brake discs with a ribbing surface can be repaired in a workshop if their remaining thickness allows it. Otherwise, replace the discs with new ones.

12. Measure the thickness of the brake disc. When the maximum permissible residual thickness is reached, replace the brake disc, see the relevant chapter.

13. Check the condition of the brake shoe retaining springs4 (see illustration 2.8) and replace them if necessary.

14. Check the condition of the brake cylinder piston seal. Replace a damaged or cracked seal immediately, because dirt that penetrates through a damaged seal will quickly cause the brake caliper to become depressurized. In this case, the brake caliper must be removed and disassembled (the work is carried out in the workshop).

15. Make sure that brake fluid does not leak from under the brake cylinder piston.

16. Check the condition and fit of the brake cylinder piston cap. If necessary, take the caliper to a workshop for overhaul or replace it with a new one.

17. Also check the condition of the dust caps on the heads of the caliper guide pins. If they are damaged, replace them.

Attention! If the brake pads are very worn, it is necessary to check the ease of movement of the brake cylinder piston. To do this, insert a wooden block into the front caliper and ask an assistant to slowly press the brake pedal. The brake cylinder piston should move easily. To check, it is necessary to install a second caliper or use a caliper from another wheel. If the piston has a hard movement, repair the caliper (the work is done in the workshop).

18. Right front outer brake shoe. Disconnect the plug connection of the brake shoe wear sensor 43. If the sensor is damaged, replace it with a new one (see illustration).

Installation

19. Press the brake cylinder piston in using a special pressing device. You can also use a wooden rod made of hard wood (hammer handle), but do not distort the piston or damage its surface or the dust cap itself (see illustration).

Caution! When the piston is pressed, brake fluid is squeezed out of the wheel brake cylinder into the expansion tank. Monitor the brake fluid level in the expansion tank and remove it if necessary.

Attention! To extract brake fluid from the expansion tank, use a siphon or a plastic bottle that is not destroyed by the brake fluid. Do not use regular drinking water bottles! Brake fluid is poisonous and should never be sucked out by mouth through a hose. Use a siphon. And after replacing the brake pads, the brake fluid level in the tank should not exceed the maximum mark, because it expands when heated. The leaking brake fluid flows down the master cylinder, destroys the varnish and causes corrosion.

20. Right front outer brake shoe. Disconnect the brake shoe wear sensor plug 1 from the groove of the old shoe 2 and connect it to the new one (see illustration).



21. Install the upper and lower retaining springs into the shoe guides.

22. Install the brake shoes into the retaining springs on the guide. The shoes are installed sideways, diagonally.

Caution! There must be no grease or oil on the surfaces of the brake disc and brake pads.

23. Carefully install the caliper into place, avoiding stress on the upper guide bolt.

24 Secure the caliper at the bottom with a new self-locking bolt 1 and tighten it to 30 Nm (see illustrations 2.5 and 2.6).

25. Tighten the lower caliper mounting bolt to the brake pad guide with a force of 30 Nm.

26. Right outer brake shoe. Install the pad wear sensor into the plug connection. If the sensor wire is long, wind it up so that it does not sag and fray.

27. Install the front wheels in accordance with the marks made during removal. Before doing this, lubricate the centering seat of the wheel disk on the hub with a thin layer of grease. Do not lubricate the wheel mounting bolts. Replace rusted bolts with new ones.

28. Screw in the wheel mounting bolts and lower the car onto its wheels.

29. Tighten the bolts in a crisscross pattern to 110 Nm.

Attention! Press the brake pedal several times until you feel a strong resistance to pressing. When you do this, the brake pads are centered and they automatically set themselves to the working position.

30. Check the brake fluid level in the expansion tank. If necessary, top up the fluid to the maximum mark.

31. Carefully break in the new brake pads. To do this, brake several times, bringing the speed from about 80 km/h to 40 km/h and pressing the brake pedal lightly. Let the brakes cool down in between. During the first 200 km of driving with new brake pads, avoid unnecessary braking until the car has come to a complete stop.

Attention! Brake linings must not be thrown away with regular garbage, as the dust that forms on them is hazardous to health. They should be disposed of only at special points.

Attention! Make sure that:

• a) the brake hoses are securely connected;
• b) brake hoses are secured in holders;
• c) the brake drive bleed nipples are screwed in;
• d) there is a sufficient volume of brake fluid in the expansion tank.

32. Perform a brake system leak test by starting the engine.

To do this, press the brake pedal with a force of 200-300 N (20-30 kg) and hold it for about 10 seconds. The pressure in the system and, accordingly, the resistance of the brake pedal, should not decrease. Check all connections for leaks.