"Gazelle" Gas-2705>> Brake system>> Maintenance service and repair of brake systems>> Repair of the main brake cylinder
Causes of defect of the main brake cylinder are deterioration or loss of elasticity of cuffs, deterioration of working surfaces of the cylinder and pistons, swelling of cuffs from hit in system of mineral oils, a contamination of compensatory apertures.

Fig. 8.3. The main brake cylinder: 1 — the case; 2 — a tube; 3 — the connecting plug; 4 — a tank; 5 — a protective cap; 6 — the gauge of a signalling device of emergency falling of level of a brake liquid; 7 — a persistent ring; 8 — an external cuff; 9 — the directing plug; 10, 17 — pistons; 11 — a lock ring; 12 — a sealing ring; 13 — a piston washer; 14, 16 — cuffs; 15, 18 persistent washers; 19 — a spring: 20 — a stopper; And, In — compensatory apertures; With — перепускные apertures

If liquid level in a tank of the main brake cylinder has decreased, and at survey of connections of pipelines and knots, including brake mechanisms, a leak of a brake liquid is not found out, in this case leak of a brake liquid is possible through an external cuff 8 (fig. 8.3 see) in cavity А1 of the vacuum amplifier.
If the brake pedal at the appendix to it of effort nearby 200—300 Н (20—30 кгс) at first moves approximately on half of course, and then under invariable effort will gradually move to a cab floor the main cuffs 14 or dividing 16 in this case are damaged. Defects of dividing cuffs can be found out, for this purpose it is necessary to merge from a tank a liquid below level of a dividing partition on 10—15 mm in each section. If after pressing a pedal of a brake of 3-5 times liquid level in sections changes, it specifies in an overflowing of a liquid from one section in another that is possible only at deterioration of dividing cuffs.
In case of swelling of cuffs occurs, as a rule, нерастормаживание systems because of overlapping by the main cuffs of 14 compensatory apertures. For definition of this malfunction it is enough to disconnect tubes from the main cylinder. If after вытекания liquids from working cavities leak stops also level in a tank does not decrease, compensatory apertures are blocked by cuffs or have got littered. In these cases the main cylinder should be removed from the car and to disassemble.
Removal and dismantling of the main brake cylinder is necessary for carrying out in a following order:
- To clear of a dirt the main brake cylinder, the vacuum amplifier and the pipelines attached to the main cylinder;
- To disconnect pipelines from the main brake cylinder and to muffle their rubber caps from prorolling valves;
- Having turned on two nuts, to remove the main brake cylinder from hairpins of a cover of the vacuum amplifier;
- To uncover 6 a tank and to merge a brake liquid;
- To turn the cylinder a tank downwards and, having pressed some times the piston 10, to remove the rests of a brake liquid from the main cylinder;
- To disconnect a tank from the main brake cylinder and to take from the cylinder case connecting rubber plugs 3 with tubes 2;
- To turn away a stopper 20, to take a spring 19 with a persistent washer 18. To press the piston 10 then the piston 17 with cuffs 14 and 16 can be taken a hand;
- To remove a lock ring 11 nippers 7814-5593 or special flat-nose pliers;

Fig. 8.10. The primary piston of the main cylinder: 1 — a spring; 2 — the holder of a spring; 3 — the screw; 4 — a persistent washer; 5 — a cuff; 6 — a washer; 7 — the piston

- To take a hand for a shaft the piston 10 in gathering. To remove from the piston directing plug 9, an external cuff 8 and a persistent ring 7. It is not recommended to unscrew needlessly the screw 3 (fig. 8.10) the holder.
After dismantling it is necessary to examine attentively details of the main brake cylinder and to be convinced that the mirror of the cylinder and working surfaces of pistons absolutely pure and on them is absent a rust, risks and other defects. At the defects causing considerable change of internal diameter of the cylinder, or at its unilateral deterioration to replace the case new.
It is recommended to replace rubber cuffs new at each dismantling of the main brake cylinder. Before assemblage of the main brake cylinder to wash out all details in spirit or a pure brake liquid. Not to suppose hit of mineral oils, gasoline, kerosene or diesel fuel on a detail as rubber cuffs can be thus damaged.
For assemblage of the main brake cylinder it is necessary:

Fig. 8.11. Installation of cuffs of the main brake cylinder: 1 — the main cuff; 2 — dividing cuffs; 3 — an external cuff

- To establish cuffs on pistons, as is shown in fig. 8.11;
- To grease a mirror of the cylinder with a brake liquid;
- To collect the primary piston 6 (fig. 8.10 see), to check up the size (190,275) mm it (is not regulated);
- To grease a cuff 14 (fig. 8.3) a fresh brake liquid see and to insert the piston 10 into the case of the main cylinder;
- To insert a persistent ring 7, the external cuff 8 directing the plug 9 and lock ring 11, using nippers or flat-nose pliers;
- To establish on the piston 17 dividing cuffs 16, a washer 13 pistons, the main cuff 14, a persistent washer 18 and a spring 19;
- To grease cuffs with a fresh brake liquid and to insert the piston into the cylinder case;
- Overcoming resistance of a spring 19, to wrap a stopper 20 with a lining;
- To establish connecting plugs 3 with tubes 2 in the cylinder case, preliminary having greased with their fresh brake liquid;
- To establish a tank 4 on connecting plugs 3;
- To establish the main brake cylinder on the vacuum amplifier, preliminary having checked up a condition of a sealing ring 12, and if necessary to replace it;
- To fill in a brake liquid in a tank and to pump over system as it is specified above.

Before installation in the main brake cylinder of new details from the last it is necessary to remove carefully консервационную greasing to exclude its hit in brake system.