34 00... General Data

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 rags which do not lose lint.
• 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 cleaning fluid, no brake cleaning fluid must enter the brake system.
• Even the most minute traces of brake cleaning fluid must be avoided.

Brake fluid: 

• Replace brake fluid at least every two years.
• Never re-use drained brake fluid.
• Always use BMW-approved brake fluid.
• Always dispose of brake fluid in approved receptacles.
• 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 linings:
  1. Brake linings should be replaced when the warning threshold of the brake lining wear indicator is replaced.
  2. Brake linings must always be replaced on both sides of any axle.
  3. The friction faces of brake linings must not come into contact with oils or grease and if brake linings become contaminated with substances of this kind, they must be replaced.
  4. 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. Brake linings with left/right markings must be installed on the respective vehicle side.
  5. 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 discs:
  1. 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.
  2. Always strip preservative off new parts before installation. With the rear brake discs, also strip preservative off brake drum on parking brake.
• Brake drums:
  1. Brake drums must not be scored or cracked; in addition, the maximum drum diameter, radial runout and surface roughness of the friction surfaces must not exceed or drop below the permitted values.
  2. Always strip preservative off new parts before installation.
• Brake calipers:
  1. Only approved pastes on the basis of glycine must be used for repairs of brake calipers.
  2. All moving parts on the brake caliper must move freely: note grease specifications.
  3. To grease the caliper guides, always use BMW-approved lubricants.

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.
• Check all connection points for leaks (seal integrity).
• Only tighten down brake hoses on the front axle when wheels are in straight-ahead 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 couplings, refer to BRAKES - TIGHTENING TORQUES .

Anti-lock braking system ABS/slip control system ASC+T: 

The ABS is essentially maintenance-free but bear in mind the following when working on vehicles with ABS systems:

• 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 electronic 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.
• Terminals must be completely tight on end poles of battery.
• Brake lines on hydraulic unit must not be swapped over: if applicable, mark them prior to disassembly.
• The ABS must be tested in accordance with the "Electrical Troubleshooting Manual" if one of the following ABS components has been removed or replaced:
  • Hydraulic control unit
  • ABS control unit
  • Wheel-speed sensor
  • ABS wiring harness
  • Valve control relay
  • Relay pump motor

  In vehicles with ASC+T, the ABS/ASC control unit must be readjusted if one of the following components has been removed or replaced:

  • ABS/ASC+T control unit
  • Throttle-valve assembly
  • Throttle potentiometer