General information on anti-blocking brake system. BMW the 5th E28/E34 series (from 1981 to 1993 of release)
Repair of BMW E28 and series E34 from 1981 to 1993
1. Cars of the BMW brand of 5-series
2. Engine
3. Cooling system
4. Power supply system
5. Ignition system
6. Control systems of the engine and decrease in toxicity of the fulfilled gases
7. System of production of the fulfilled gases
8. Coupling
9. Manual box of gear shifting (RKPP) and automatic transmission (AT)
10. Transmission line
11. Steering and suspension bracket
12. Brake system
12.1. General information
12.2. General information on anti-blocking brake system
12.3. Replacement of blocks of disk brake mechanisms
12.4. Removal, major maintenance and installation of a support of the disk brake mechanism
12.5. Survey, removal and installation of a brake disk
12.6. Replacement of boots of drums of brake mechanisms
12.7. Removal and installation of the main brake cylinder
12.8. Condition check, removal and installation of the vacuum amplifier of brakes
12.9. Description, removal and installation of the vacuum hydraulic booster of brake system
12.10. Replacement of a cable (cables) of a drive of the parking brake
12.11. Adjustment of the parking brake
12.12. Condition check, removal and installation of assembly of the parking brake
12.13. Adjustment of a pedal of a brake
12.14. Check and adjustment of the switch of a stoplight
12.15. Survey and replacement of brake lines and hoses of hydraulic system of brakes
12.16. Pumping of hydraulic system of brakes
12.17. Diagnostics of malfunctions of brake system
13. Body
14. Control body sizes
15. Heater and air conditioner
16. System of onboard electric equipment
17. Routine maintenance of the car
18. Size table and adjusting data
19. Schematic electric circuits
20. Governing bodies and operation receptions
21. System of onboard diagnostics - a principle of functioning and codes of malfunctions


12.2. General information on anti-blocking brake system

The anti-blocking brake system is developed to provide maneuverability of the car, its stability on the road and an optimum mode of braking at emergence of a difficult road situation on any paving. The system supervises speed of rotation of wheels and operates pressure in brake system in the course of braking. It prevents premature blocking of wheels.

The ABS system consists of three main components - sensors of speed of rotation of wheels, the electronic control unit and the control unit hydraulics. Sensors (since 1985 - on one on each wheel, and on earlier models - on both forward wheels and on back differential) send one signals of various tension on the control unit which traces these signals, compares them to information put in the program, and defines, whether the wheel is going to be blocked. If it so, the control unit sends a signal to the control unit hydraulics to reduce pressure of liquid (or not to raise any more it) in a brake support of this wheel. Modulation of pressure is made by means of electric valves of the solenoid.

If there is a malfunction in the system, on the dashboard the alarm lamp of "ABS" lights up. Sometimes it is possible to define a cause of defect of ABS system visually. Attentively examine system conducting. Pay special attention to conducting and connections at each wheel. Look for signs of an istiraniye or other damages caused by the wrong laying of wires. If conducting of the wheel sensor is damaged, it is necessary to replace the sensor (conducting and the sensor are inseparable).

DO NOT TRY to repair ABS system conducting. This system is sensitive to the slightest changes of resistance. Repair of conducting can change size of resistance and lead to system misoperation. If conducting of system is somehow damaged, it is necessary to replace it.

Before shutdown or connection of any electric connections make sure that ignition is switched off.

Diagnostics and repair

If in the course of operation of the car on the dashboard there was included an alarm lamp, means, it is necessary to pay attention to ABS system. Though special test devices are necessary for the correct diagnostics of system, you can make some preliminary checks before sending the car in dealer office of service.

  • Check level of brake liquid in the tank.
  • Check electric sockets of the electronic control device.
  • Check electric sockets of the control device of hydraulics.
  • Check safety locks.
  • Check the conducting going to each forward and back wheel and make sure that all connections in an order and conducting is not damaged.

If the above described preliminary check did not eliminate a problem, it is necessary to send the car in dealer office of service for diagnostics. As this system is very difficult, its repair is necessary for making only in dealer office of service.

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12.1. General information
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12.3. Replacement of blocks of disk brake mechanisms