9.10.2. Filling with liquid of the brake system. Removal of air from the brake system (pumping)
The brake system is pumped over when replacing brake fluid, at hit in an air hydraulic actuator, when carrying out the repair work connected with depressurization of system.
The hydraulic drive has two independent contours therefore each contour is pumped over separately. Pumping should be begun with the brake mechanism, the most remote from the main brake cylinder, that is with right. Pumping is carried out by two performers in the following order:
Fig. 8.3. Main brake cylinder: 1 — the case; 2 — a tube; 3 — the connecting plug; 4 — a tank; 5 — a protective cap; 6 — the sensor of a signaling device of emergency falling of level of brake fluid; 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 — compensation openings; With — perepuskny openings
- to unscrew the sensor 6 (see fig. 8.3) and to fill in in a tank the 4th brake fluid to a tag the MOVE;
- to clear valves of pumping of lobbies and back brake mechanisms of dirt, to remove rubber protective caps from pumping valves;
- to put on a hose of discharge of brake fluid a head of the valve of the right back wheel cylinder. To lower the free end of a hose in the brake fluid poured in a pure transparent vessel;
- to unscrew the pumping valve on 1/2 — 3/4 turns, to press a brake pedal. In the provision of completely pressed pedal, the assistant has to wrap the pumping valve. To repeat this operation until allocations of vials of air stop;
- after the pumping termination the assistant has to wrap densely the valve while the pedal of a brake keeps in the pressed situation. To remove a hose and to put on a protective cap;
- in the same sequence to pump over back left and forward brake mechanisms.
During removal of air from a hydraulic actuator of brakes it is necessary to add in due time brake fluid in a tank, without allowing a "dry" bottom.
After pumping to add brake fluid in a tank to a tag the MOVE. If pumping is executed insufficiently carefully, then when pressing a brake pedal at the end of its course some elasticity, big or smaller depending on amount of the air which remained in system will be felt. The pedal course at the same time increases a little. In this case it is necessary to repeat pumping.
Replacement of brake fluid
Replacement of brake fluid in system is necessary as it at operation absorbs moisture from the atmosphere, than worsens the temperature properties and causes corrosion of cylinders and pistons. Replacement of liquid is made at seasonal service of the car (once a year).
It is necessary for replacement of brake fluid:
- to turn off a tank cover from the main brake cylinder, to remove protective caps from pumping valves;
- to put on heads of valves rubber hoses which free ends to lower in transparent vessels, and then to unscrew all valves on 1/2 — 3/4 turns;
- to merge the fulfilled liquid from system, vigorously pressing a pedal of a brake and smoothly releasing it. In process of the termination of the expiration of the fulfilled liquid to wrap pumping valves;
- to merge the fulfilled liquid from vessels and to put them into place under rubber hoses; to fill in fresh brake fluid in a tank of the main brake cylinder and to unscrew all valves of pumping. Vigorously pressing and smoothly releasing a brake pedal, and also in due time filling up a tank with brake fluid, to fill system with fresh brake fluid; in process of emergence in vessels of pure brake fluid to wrap pumping valves;
- to pump over system by the technique described above.