Air that gets into the brake hydraulic system when replacing pipes, hoses, sealing rings, or when the system is leaking causes an increase in the working stroke of the brake pedal, its "softness", and significantly reduces the effectiveness of the brakes.
Before removing air from the brake system, make sure that all brake drive units and their connections are tight, check and, if necessary, fill the reservoir to the normal level with Neva or Tom liquid. Then thoroughly clean the air removal nipples from dirt and dust and remove the protective caps from them.
Air is removed first from one circuit, then from the other, each time starting from the wheel furthest from the main cylinder. Bleeding of the hydraulic drive is carried out in the following order:
- remove the front wheels; a rubber hose is placed on the head of the fitting 1 (Fig. 143), and the other end of the hose is lowered into a transparent container partially filled with brake fluid;
- sharply pressing the brake pedal 3-5 times with intervals of 2-3 seconds between presses, unscrew the nipple 1 by 1/2-3/4 of a turn with the pedal pressed. Continuing to press the pedal, displace the liquid in the system together with the air through the hose into the vessel;
- its forward position and the flow of liquid through the hose stops, tighten the air release nipple until it stops. These operations are repeated until bubbles stop coming out of the hose;
- holding the pedal in the pressed position, tighten the nipple until it stops and remove the hose, wipe the nipple dry and put on the protective cap;
- repeat the operations for the other wheels, first on the second wheel of the same circuit, and then sequentially on both wheels of the second circuit.
When removing air, maintain a normal fluid level in the brake hydraulic drive reservoir. After completely removing air, the brake pedal should not move more than 1/2-3/4 of its travel.
To eliminate the influence of the pressure regulator on bleeding the brakes, air is removed with the rear wheels loaded (hanging the rear of the vehicle is not allowed).
If the liquid has been drained completely, then before removing air from the system:
- unscrew the fittings on the cylinders of all wheels by 1.5-2 turns;
- sharply pressing the brake pedal and slowly releasing it, tighten the nipples as the liquid flows out of them. Then bleed the drive as described above.
If, even after prolonged removal, air continues to come out of the hose in the form of bubbles, it means that it enters the system through damage in the pipelines, due to insufficient tightness of the connections, or as a result of a malfunction of the main or wheel cylinders.
If air removal is performed on a vehicle whose brake system has been in operation for a long time, the fluid in the system is replaced with new fluid.
[The original is on the portal www.VAZbook.ru]