Brakes and Traction Control: Service Precautions

General Data
The brake system is one of the most important safety systems in a motor vehicle. It is therefore essential to act with utmost care when working on the brake system and to follow the instructions below.

General:
- Ensure cleanliness and only use rags which do not lose lint.
- Wash off or vacuum off brake dust, do not blow clear with compressed air. Dust is damaging to health.
- Do not under any circumstances allow oils or greases to get into the brake system; this would result in a complete breakdown of the brake system.
- When cleaning brake components with brake cleaner do not under any circumstances allow brake cleaner to get into the brake system.
Refer to BMW Parts Service,
- Even the most minute traces of brake cleaner must be avoided.

Brake fluid:
- Change brake fluid at least every two years.
- Never re-use drained brake fluid.
- Use only BMW-approved brake fluid.
Refer to BMW Service Operating Fluids.
- Dispose of brake fluid in approved apparatus only.
Refer to BMW Service Workshop Equipment & Planning Documentation.
- Do not allow brake fluid to drain into drain pipes, into the outside environment or into unsuitable facilities. This would create the risk of groundwater contamination since brake fluid is classed as a fluid that is hazardous to water.
- Do not allow brake fluid to come into contact with the vehicle's paintwork as this would damage the paintwork.
- Brake fluid must not be allowed to remain on bare skin too long in order to avoid skin problems. Wash skin coated with brake fluid with water and soap.
- If brake fluid gets into your eyes, rinse them immediately with plenty of clean water and seek medical attention (eye specialist).

Wheel brakes:
Brake linings:
Brake linings should be replaced when the warning threshold of the brake lining wear indicator is replaced.

Refer to Technical Data.

Brake linings may only be replaced for their respective axles.

The friction surfaces of the brake linings must not come into contact with oils or greases; the brake linings must be replaced if they are fouled by such substances.

In the case of rotation-dependent brake linings, make sure the arrow marking points in the direction of rotation of the brake disk for when the vehicle is moving forward. Fit brake linings with left/right markings on the appropriate sides of the vehicle.

One-sided angled areas on the brake linings must be located on the disk contact side of the brake caliper for when the vehicle is moving forward.

Brake disks:
Brake disks must not be scored or cracked; in addition, the minimum disk thickness, disk run-out, parallelism and surface roughness of the friction surfaces must not exceed or drop below the permitted values.

Refer to Technical Data.

Dewax new components thoroughly before installation; on the rear brake disks, this should also be done on the brake drum of the parking brake.

Brake drums:
Brake drums must not be scored or cracked; in addition, the minimum drum diameter, radial run-out, parallelism and surface roughness of the friction surfaces must not exceed or drop below the permitted values.

Refer to Technical Data.

Dewax new components thoroughly before installation.

Brake calipers:
Only approved pastes on the basis of glycine must be used for repairs on brake calipers.

All moving parts on the brake caliper must demonstrate ease of movement, observe lubrication instructions.

To grease the caliper guides, use only BMW-approved lubricants.
Refer to BMW Service Operating Fluids).

Brake lines, brake hoses:
- Brake lines and brake hoses must be correctly routed and must not touch or scuff against the body or other components.
- To prevent damage, release and tighten brake line couplings with a special brake line wrench only.
- The system must be bled each time any brake lines have been detached.
- Check all joints and connection point for leaks.
- Tighten down the brake hoses on the front axle only when the wheels are in the straight-ahead driving position.
- Seal off open connections of brake lines and individual components so as to prevent any contaminants from getting into the brake system.
- When tightening down brake line couplings, observe tightening torques.
Brake hose couplings
M10x1 18 ± 1 Nm
M12x1 14 ± 1 Nm

Wheel-slip control system:
The wheel-slip control system is essentially maintenance-free; however the following must be observed:
- When carrying out welding work with electric welding equipment, be sure to disconnect the plug from the electronic control unit (ignition turned off).
- Electronic control unit may be briefly subjected to max. 95°C and to max. 85°C for a longer time (approx. 2 hours) when painting vehicle.
- Terminals must be completely tight on end poles of battery.
- The brake lines on the hydraulic unit must not be mixed up; if necessary, mark them before they are removed and after completing repairs perform the mix-up check with the DIS Tester.