10.5. Main brake cylinder

Removal, dismantling and installation

Section of the main brake cylinder of standard type

1 — a sealing stopper
3 — the piston (primary contour)
4 — a persistent washer
5 — a lock ring
6 — the secondary and vacuum plug
7 — an intermediate ring
9 — a pro-masonry washer
10 — primary plug
11 — a basic ring
12 — the holder of a spring

14 — the connecting screw
15 — the lock screw
17 — a compression spring
18 — the dividing plug
20 — the piston (a secondary contour)
21 — a compression spring
22 — the case
And — an opening for removal of leaks
In — a jellied opening
With — the compensating opening

Section of the main brake cylinder with pressure difference sensor

3 — the piston (primary contour)
20 — the piston (a secondary contour)
35 — the operating piston
36 — the ring plug
37 — a spring
38 — the holder of a spring

39 — the screw
40 — a sealing ring
41 — the sensor
42 — a switching off rod

Electric (And) and hydraulic (In) connections of the main brake cylinder and a fixing nut (C)


  1. Prepare a workplace to exclude hit of brake fluid on paint and varnish surfaces.
  2. Disconnect and at once close a cap (adhesive tape) the hydraulic line from the main brake cylinder.
  3. Disconnect a wire from pressure difference sensor.
  4. Disconnect from a tank a hydraulic hose of the mechanism of the drive of coupling (for cars with the manual transmission).
  5. Turn off nuts and remove the main cylinder from an end face of the vacuum amplifier.
  6. Take out a sealing ring from a flute of a flange of the main cylinder.
  7. Clear the external surfaces of the main cylinder, using alcohol-denatured alcohol or liquid for cleaning of brakes.
  8. Remove a tank of brake fluid together with a sealing stopper.
  9. Merge brake fluid from a tank in pure capacity.
  10. Slightly wring out the main piston and turn out the lock screw.
  11. Take out a spring lock ring, take the piston, lock washers, an intermediate ring, auxiliary and vacuum couplings; for removal easy percussion about a wooden surface is allowed.
  12. Remove the sensor of difference of pressure, having turned off a face stopper, easy percussion take the operating piston.
  13. Turn off a cover of a tank of brake fluid and remove the mesh filter.
  14. Carry out cleaning of details and their fault detection. Pay special attention to the surfaces of pistons and cylinders, if necessary replace.
  15. Manually install new consolidations on pistons.
  16. Grease the internal surfaces of the main cylinder and dip main, auxiliary and operating pistons in pure brake fluid.
  17. Using an assembly mandrel, enter details of the 1st and 2nd contours into the cylinder. When carrying out operation manually pay special attention to occurrence of consolidations, the bend is not allowed.
  18. Slightly press on a rod of the main piston, insert and delay the lock screw with new consolidation.
  19. Insert the operating piston similarly, delay a face stopper with new consolidation.
  20. Clear the filter in fresh (pure) brake fluid, insert it into a tank and screw a jellied stopper.
  21. Press sealing traffic jams in the main cylinder and install on it a tank, having pressed it at first on one stopper, then having turned on 180 ° and having pressed on other stopper.
  22. Connect a wire to the indicator of pressure difference and the indicator of low level of liquid.
  23. Connect hoses and tighten connecting nuts.

See also Vacuum amplifier of a brake.