Causes of air can be damaged brake pipes (usually at the points of connection or fastening to the body), loss of tightness of brake hoses (mechanical damage or loose connection), damage to the cuffs in the working and / or in the main brake cylinders, as well as any repair of the brake system components.
The ingress of air into the system reduces the efficiency of its work and, consequently, traffic safety.
Before carrying out the operation to remove air, carefully clean the places around the bleeder fittings and the stopper of the brake fluid reservoir, add brake fluid to the reservoir.
Choose an elastic, preferably transparent tube that fits snugly on the bleeder fitting (usually take tubes from medical blood transfusion systems).
If the work was carried out only with the brake of one wheel, then it is enough to pump only this part of the hydraulic drive. In other cases, the following order should be followed: rear right wheel, rear left, front right, front left.
Put the tube on the bleed valve of the wheel cylinder, lower the other end of the tube into the vessel (also preferably transparent) with a capacity of about 200 ml, half filled with brake fluid.
The simplest is the method in which one person creates pressure in the system by pressing the brake pedal several times and then holding it down. The second person unscrews the fitting.
Attention! Unscrew the fitting only when the pedal is depressed!
When the fitting is unscrewed, the brake fluid with air exits through the hose into the vessel. Air bubbles rise to the surface of the liquid in the vessel, and the liquid itself plays the role of a valve, not letting air back into the system when the pedal is accidentally released. Tighten the fitting and pressurize again. Bleed until no air comes out of the system. Pumping for all wheels is done in the same way. Constantly add brake fluid to the reservoir; if the liquid level in it drops significantly, then pumping will have to be repeated. If you do not have an assistant, you need to pick up a rail of such length that it can fix the pedal in the depressed state, resting one end of it on the pedal and the other in a convenient place on the body (e.g. seat).
More complicated is the method in which the pressure in the system is created by supplying compressed air to the tank at a pressure of not more than 1 kg / m2. It is not necessary to press the pedal in this case, all other actions are similar to those described above.
The liquid drained from the system can only be used again if it is clear and its use period does not exceed 1.5 years (and only after filtering).
When changing the brake fluid, proceed in the same way as when removing air from the system. The criterion for stopping pumping should be considered the appearance of fresh liquid in a transparent tube (it is clearer than the old one).
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