BMW X3 Service & Repair Manual: General notes

The brake system is one of the most important safety systems in the vehicle. Therefore, it is important to exercise special care when performing repair work on the brake system and to adhere to the following instructions.

• Ensure cleanliness and use only 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.
• Oil or grease must never enter the brake system. This would result in failure of the entire brake system.
• When cleaning brake components with brake cleaner, never let brake cleaner enter the brake system.
• Even a minute amount of brake cleaner residue must be avoided.
• Replace brake fluid at least every two years.
• Important: Never reuse drained off brake fluid.
• Use only BMW-approved brake fluid.
• Dispose of brake fluid in approved appliances only.
• 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.
• Brake pads: Brake pads must be replaced when the remaining brake pad thickness is reached.

  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 oil or grease. The brake pads must be replaced if they are dirt contamination 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, disc runout, parallelism and surface roughness of the friction surfaces must not exceed or drop below the permitted values.

  Always strip preservative off new parts before installation. With the rear brake discs, also strip preservative off brake drum on parking brake.

• 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 components on the brake caliper must move freely: note grease specifications.

  Use only BMW-approved lubricants to grease the brake caliper guides.

• 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 TORQUE when tightening down brake line couplings.

  The traction control system is basically maintenance-free. However, be sure to adhere to the following:

• When carrying out welding work with electric welder, be sure to disconnect the connector from the electronic control unit (ignition turned off).
• During painting work, the control unit may be subjected for brief periods to max. 95 ºC and for long periods (approx. 2 hours) to max. 85 ºC.
• Battery clamps must be completely tight on battery terminals.
• The brake lines on the hydraulic unit must not be mixed up; if necessary, mark them prior to disassembly.
• On completion of repair work, carry out mix-up test with the DIS diagnosis system.