BMW 3 Series E30

since 1983-1994 release

Repair and operation of the car

+ 1. Maintenance instruction
+ 2. Maintenance
+ 3. Engine
+ 4. Cooling system
+ 5. Heating and ventilation
+ 6. Fuel system
+ 7. Exhaust system
+ 8. Transmissions
+ 9. Coupling
- 10. Brake system
   10.2. Specifications
   10.3. Anti-blocking system (ABS)
   10.4. Blocks of disk brakes
   10.5. Support of a disk brake
   10.6. Brake disk
   10.7. Blocks of drum brakes
   10.8. Main cylinder of brakes
   10.9. Vacuum amplifier of brakes
   10:10. Cable(s) of the emergency brake
   10:11. Adjustment of the emergency brake
   10:12. Mechanism of the emergency brake
   10:13. Brake pedal
   10:14. Braking signal switch
   10:15. Hoses and lines of a hydraulic actuator of brakes
   10:16. Removal of air from a hydraulic actuator of brakes
+ 11. Running gear
+ 12. Body
+ 13. Electric equipment
+ 14. Useful tips


10.8. Main cylinder of brakes



It is recommended to replace the removed cylinder new or restored as in case of liquid dribble replacement of details of the old cylinder with new details from a remkomplekt does not yield positive result. As a rule, old cylinder will be strongly worn-out what it will be possible to be convinced of, having spent considerable time for its dismantling.

Main cylinder and vacuum amplifier of brakes

1. Nutritious tank
2. A tank stopper with the switch of a control lamp of level
3, 6. Vacuum hose
4. Collar
5. The backpressure valve (on models 325i)
7. Collar
8. The backpressure valve (on all models except 325i)
9. Bracket
10. Pusher fork
11. Axis
12. Nut
13. Cover
14. Washer
15. Quencher of pulsations
16. Pusher
17. Filter
18. Sealing ring
19. Restrictive bolt
20. Main cylinder
21. Nuts of fastening of the main cylinder
22. Tank sealant
23. Collar
24. Vacuum amplifier of brakes
25. Knee


The main cylinder with the attached vacuum amplifier take place in the left part of a motor compartment.

1. To remove the main cylinder, disconnect the conducting socket (shooter from above), disconnect hydraulic actuator tubes (lower right arrow) of and turn off two bolts of fastening (lower left arrow).
2. Remove as much as possible brake fluid from a tank.
3. Turn off the union of tubes of a hydraulic actuator on the main cylinder, immediately muffle tubes and openings. Take tubes aside.
4. Disconnect sockets from the main cylinder, turn off nuts of fastening of the cylinder to the vacuum amplifier and remove the cylinder. Remove and replace a sealing ring (1).

Removal of air from the main cylinder

1. Before installation of the new or restored cylinder it needs to be pumped over on the special machine. For this purpose fix the cylinder in a vice through soft laying (otherwise the cylinder can burst!).
2. Establish caps with a carving in openings of unions of tubes of a hydraulic actuator and slightly bring up them that through them there did not pass air.
3. Fill a tank with brake fluid of the recommended type.
4. Remove one of caps and enter the piston into the cylinder, having pushed it the screw-driver to remove air.
5. Without releasing the piston, tighten a cap.
6. Repeat the procedure until brake fluid without air bubbles does not begin to follow from an opening under the union. Constantly add brake fluid in a tank of the main cylinder.
7. To accelerate the procedure of preliminary pumping of the cylinder it is possible to muffle an opening under the union a finger, however upon termination of the procedure tighten a cap and repeat the procedure on other opening.


1. Install the main cylinder (together with a new sealing ring) and wrap by hand fastening nuts.
2. Turn the union of tubes of a hydraulic actuator, without making considerable efforts.
3. Tighten everything the union and a nut of fastening with the set moment.
4. Fill the main cylinder with liquid, then pump over it (if preliminary pumping was not carried out), pump over all hydraulic actuator.
5. When pumping the cylinder on the car ask the assistant to press several times a pedal and to hold it in the pressed situation. Release the union to allow to leave to air and liquid, then tighten. Repeat the procedure for both unions until in brake fluid vials of air do not disappear. Check work of brakes before operation of the car.