Front Brake Caliper — Removal, Repair and Installation (BMW 3 Series E46)

Note: Before starting work, read the note at the beginning of paragraph 2 about the dangers of brake fluid, and the warning at the beginning of paragraph 4 about the dangers of asbestos dust.

If the piston cannot be pulled out by hand, it can be pushed out by connecting a compressed air hose instead of the brake hose. Use only low pressure, such as from a tire pump. When pushing the piston out, make sure that your fingers do not get caught between the piston and the caliper.

Removal

1. Apply the parking brake. Raise the rear of the vehicle and support it on jack stands (see "Raising and Supporting the Vehicle on Jack Stands"). Remove the appropriate wheel.

2. Minimize fluid leaks by clamping the flexible hose.

3. Clean the area where the hose connects to the caliper. Then loosen the brake hose nut on the caliper.

4. Remove the brake pads (see paragraph 4).

5. Unscrew the caliper from the hose and remove it from the vehicle.

Repair

6. Install the support on the workbench. Clean it from dust and dirt. Do not inhale dust - it is dangerous to health.

7. Pull the piston out of the caliper. Remove the dust seal.

8. Using a small screwdriver, remove the piston seal without damaging the cylinder bore (Fig. 8.8).



9. Clean all parts thoroughly. Use only methyl or isopropyl alcohol or clean brake fluid. Never use gasoline or kerosene-based solvents, as they corrode the hydraulic seals. Dry the components immediately after cleaning with compressed air or a clean, lint-free cloth. Blow out the fluid passages with compressed air.



10. Check all components and replace any that are worn or damaged. Inspect the cylinder bore and piston in particular. If they are scored, worn or corroded, replace them (in this case the entire unit is replaced). Also check the condition of the guide pins and their bushings. There should be no damage to the pins and both pins should have a fairly tight fit in the bushings. If you are not sure about the serviceability of any component, replace it.

11. If the unit is suitable for further use, purchase the appropriate repair kit. Such kits are available in various versions from dealers. All rubber seals must be replaced. They should never be reused.

12. Before assembly, make sure all parts are dry and clean.

13. Dip the piston and its sleeve in clean brake fluid. Wet the inner surface of the cylinder with clean brake fluid.

14. Insert the piston seal into the cylinder groove using only your hands (without tools).

15. Install a new dust seal on the piston. Press the outer edge of this seal into the groove of the caliper. Carefully insert the piston all the way into the cylinder, making rotational movements with the piston

Installation

16. Screw the caliper onto the brake hose.

17. Install the brake pads (see paragraph 4).

18. Tighten the brake hose nipple nut securely.

19. Remove the clamp from the brake hose or remove the plastic film from under the master cylinder bank cap. Bleed the brake system (see paragraph 2). Please note that if you have taken precautions to prevent air from entering the brake system, it is sufficient to bleed only the corresponding brake cylinder of the front wheel.



20. Install the wheel, lower the vehicle to the ground and tighten the wheel mounting bolts to the specified torque. When finished, check the brake fluid level in the reservoir and top it up to the required level (see "Weekly Checks").