Brakes and Traction Control: Service and Repair
34 00 ... General Information
The brake system is one of the most important safety systems on any 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 fluff-free cleaning cloths.
- Wash away or vacuum up brake dust, do not clear it away using compressed air. This dust is a health hazard.
- Ensure that no oils or grease enter the brake system: these substances would cause complete failure of the entire brake system.
- When cleaning brake components with brake cleaner (refer to BMW Parts Department), do not allow brake cleaner to get into the brake system.
- Even the most minute traces of brake cleaner must be avoided.
Brake fluid:
- Replace brake fluid at least every two years.
- Never reuse drained brake fluid.
- Always use BMW-approved brake fluid, refer to BMW Service Operating Fluids.
- Always dispose of brake fluid in approved receptacles, refer to BMW Service Workshop 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 paintwork as this will destroy the paint.
- 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 makes contact with eyes, immediately flush with large quantity of clean water and visit eye doctor.
Wheel brakes:
- Brake pads:
Brake pads must be replaced when the warning threshold value of the brake pad wear indicator is reached.
Refer to Technical Data.
Brake pads must always be replaced on both sides of any axle.
The friction surfaces of the brake pads must not come into contact with oils or greases. The brake pads must be replaced if they are fouled by such substances.
In the case of rotation-dependent brake pads, make sure the arrow marking points in the direction of rotation of the brake disc for when the vehicle is moving forward. Brake pads with left/right markings must be fitted on the relevant side of the vehicle.
One-sided angled areas on the brake pads must be located on the disc contact side of the brake caliper for when the vehicle is moving forward.
- Brake discs:
Brake discs must not be scored or cracked. Furthermore, minimum brake disc thickness, brake disc runout, parallelism and surface roughness of the friction surfaces must not exceed or drop below the permitted values.
Refer to Technical Data.
Always strip preservative off new parts before installation. With the rear brake discs, also strip preservative off brake drum on parking brake.
- Brake drums:
Brake drums must not be scored or cracked. Furthermore, the maximum drum inside diameter, radial runout and surface roughness of the friction surfaces must not exceed or drop below the permitted values.
Refer to Technical Data.
Always strip preservative off new parts before installation.
- Brake calipers:
Only approved glycol-based assembly pastes may be used for repairs on brake calipers.
All moving parts on the brake caliper must move freely: note grease specifications.
Use only BMW-approved lubricants to grease brake caliper guides (refer to BMW Service Operating Fluids).
Brake lines, brake hoses:
- Brake lines and brake hoses must be correctly routed and must not abut with body or components in a way which would cause chafing.
- 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.
- All connection points must be checked for leaks.
- Only tighten down brake hoses on the front axle when wheels are in straight-ahead driving position.
- Close open connections on brake lines and individual components to prevent dirt from entering the brake system.
- Observe tightening torques when tightening down brake line screw connections.
Tightening torque, 34 32 1AZ. 00 00 Excerpt From Company Standard BMW GS 90003-2
Traction control system:
The traction control system is basically maintenance-free.
However, be sure to adhere to the following:
- When carrying out welding work with electric welding equipment, be sure to disconnect the plug from the electronic control unit (ignition turned off).
- During painting work, the control unit may be subjected for brief periods to loads of max. 95 °C and for long periods (approx. 2 hours) to loads of max. 85 °C,.
- Tighten down the battery terminals completely.
- 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.
