Front disc brake caliper
1 - support
2 - guide
3 - bolt, 110 Nm
4 - dust cap
5 - fitting for removing air
6 - guide pin
7 - cork
8 - lock spring
9 - wear sensor
10 - caliper sealing kit
11 - guide bush repair kit
12 - brake pads (asbestos-free)
Withdrawal
1. Mark with paint the position of the front wheel relative to the hub. This will allow the balanced wheel to return to its original position. Loosen the wheel bolts with the vehicle on the ground. Raise the front of the car and remove the wheel.
If the brake pads are to be reused, they must be marked when removed. It is not allowed to interchange the pads of the right and left wheels. This can lead to uneven braking. Only brake pads from BMW or brake pads approved by BMW must be used. Be sure to replace all front disc brake pads at the same time, even if one of the pads has reached the wear limit.
2. Disconnect the wear indicator connector -1- at the left caliper. Do not pull on the cable.
3. Press out the bracket with a screwdriver.
4. Remove the plastic caps of the mounting bolts with a screwdriver (arrows in the illustration).
5. Remove both screws under the plastic caps using a socket wrench.
6. Remove the caliper back from the bracket and hang it on the wire to the suspension.
Do not disconnect the brake hose. Otherwise, after installation, it will be necessary to remove air from the system. Make sure that the hose is not subjected to tensile loads.
7. Remove the outer brake shoe.
8. The inner brake shoe is fixed with a spring -6- in the brake piston. Remove the brake pad.
Installation
Do not depress the brake pedal after removing the brake pads. Otherwise, the brake will be squeezed out of the housing.
1. Check the pad wear sensor. If the insulation of the contact plate is frayed, the cable insulation is damaged, or the plastic element is worn, the wear sensor must be replaced.
2. Clean with a light metal brush or wipe with a cloth soaked in alcohol, the guide surface or pad seat in the body shaft. Do not use solvents containing mineral oils or sharp-edged tools for this. If the pads are to be used again, they must also be cleaned.
3 Before installing the pads in place, check the brake disc with your fingers for marks. If damage is found, the disc should be replaced.
4. Measure the thickness of the brake disc, refer to Section Measuring the thickness of the brake disc.
5. Check the dust cap at the brake piston -2- for cracks. In the presence of cracks, replace the cap immediately, as the ingress of dirt quickly leads to loss of tightness of the caliper. To do this, the caliper must be removed and disassembled (service station work).
6. Push in the piston using the appropriate tool. This can be done with a block of hardwood (hammer handle). When doing this, pay special attention to ensure that the piston is not warped and that the piston surface and the dust cap are not damaged.
- When the pistons are pushed out of the brake cylinders, the level in the brake fluid reservoir rises. Keep an eye on the level, if necessary, suck out the liquid.
- To suck out the brake fluid, use a special or plastic bottle that is intended only for this purpose! Do not use drinking water bottles for this! Brake fluid is poisonous and must never be sucked out by mouth through a hose. Use a special device for this. After replacing the brake pads, the fluid level in the reservoir should not be above the MAX mark, as the fluid expands when heated. Leaking brake fluid flows down the master cylinder, damaging paintwork and causing corrosion.
- With a lot of wear on the brake pads, check the ease of movement of the piston. To do this, insert a wooden block into the caliper and ask an assistant to slowly depress the brake pedal. The brake piston should slide in and out easily. To carry out the check, all other supports must be inserted into their places. Make sure that the piston does not come out completely. If the piston stroke is heavy, the caliper needs to be repaired (service station work).
- Cover the adjacent surfaces of the caliper with an anti-squeal paste.
- To eliminate the squeal of disc brakes during operation, some places on the caliper must be covered with a thin layer of special paste, for example, "Never Seez Compound".
- The paste must never come into contact with dust seals, friction surfaces of the brake pads or the brake disc. If necessary, immediately wipe the paste with alcohol, replace the dust cuff with a new one. Do not cover the brake pad shim with paste.
7. Lubricate with a thin layer of anti-squeal paste the adjacent surface of the brake piston to the brake shoe.
8. Clean the adjacent surfaces -1- and -2- of the T-heads of the brake shoe at the caliper and cover with a thin layer of anti-squealing paste.
9. Clean the adjacent surface -3- of the caliper and cover with a thin layer of brake anti-squeal paste in the places shaded in the illustration.
10. Clean the bracket at the guide T-heads (arrows in the illustration) and apply a thin layer of anti-squealing paste in the areas shaded in the illustration.
11. Insert the brake shoe with the spring into the piston.
12. Insert the outer block -9- into the caliper and place the caliper on the guide. Make sure pads are clean.
13. Check up visually two bolts of fastening of a support, if necessary clear a bracket of pollution. If necessary, go through the threads in the bracket with a tap. Replace bolts with rust or damaged threads. Fasten the bolts with a 7 mm socket wrench to a torque of 30 Nm.
Just clean the bolts, they do not need to be lubricated.
14. Replace the protective caps of the mounting bolts.
15. Dock on the left side of the car the brake pad wear indicator sensor connector. The wire must pass through the loop of the bleed valve cover.
16. Install the bracket on the caliper.
17. Reinstall the wheel so that the marks made during removal match. Lubricate the seat of the wheel disk on the hub with a thin layer of bearing grease. Do not grease wheel bolts. Replace rusty bolts with new ones. Fasten the wheel with bolts. Lower the vehicle onto the wheels and tighten the bolts crosswise to 100 Nm.
In a standing position, press the brake pedal hard several times until resistance is felt. Thus, the brake pads will lie against the brake disc and take their working position
18. Check up a brake liquid in the tank, if necessary add it to the MAX mark.
- Is the brake hose secured in the holder?
- Are the bleed fittings tight?
- Has sufficient brake fluid been added?
- With the engine running, check for leaks. To do this, press the brake pedal with a force of 200 - 300 N (20 - 30 kg) within 10 s. The pedal must not loosen. Check all connections for tightness.
Carefully let the new brake pads run in. To do this, brake the car several times from a speed of 80 to 40 km / h by lightly pressing the pedal. Let the brake cool down between braking.
Brake discs must be disposed of as special material in some regions. Local authorities inform drivers about possible disposal sites.