Before removing air from the brake system, make sure that all brake drive units and their connections are tight, clean the cover and the surface around the reservoir cap, fill the reservoir with liquid «Dew» or «Tom» to the lower edge of the filler neck. Then the fittings are cleaned to remove air and the protective caps are removed from them. It is not recommended to use the fluid drained from the system to fill the tank, as it is saturated with air, has a lot of moisture and may be contaminated. Air is removed first from one circuit, then from another, starting with the rear brake wheel cylinders. Remove the cap from the fitting, put it on the head of the fitting 2 (pic. 125) rubber hose 3 for draining the liquid, and its free end is lowered into a transparent vessel 4, partially filled with liquid, so that it is immersed in the liquid. By sharply pressing the brake pedal 385 times at intervals of 2-3 s, the fitting is unscrewed by 1/2-3/4 turn with the pedal depressed. Continuing to press the pedal, the liquid in the system is displaced along with air through the hose into the vessel. After the brake pedal reaches the front end position and the outflow of fluid through the hose stops, wrap the air outlet fitting to failure, while holding the brake pedal in the depressed position. Repeat these operations until no more bubbles come out of the hose.
While holding the pedal down, tighten the fitting to failure and remove the hose. Wipe dry the fitting and put on a protective cap. Then the operations are repeated for other wheels, first on the second wheel of the same circuit, and then successively on both wheels of another circuit. When air is removed, the presence of liquid in the tank is monitored, not allowing its bottom to be exposed, since air will again enter the system. If there is no air in the brake actuator, the brake pedal should travel approximately 1/2 of its travel with the engine running. To eliminate the influence of the vacuum booster on the pumping of the brakes, the removal of air is carried out with the engine off.
If there is no brake fluid in the hydraulic drive, then fill the system as follows:
- unscrew 1.5-2 turns of the fitting on the cylinders of all wheels;
- sharply pressing the brake pedal and gently releasing it, wrap the fitting as fluid flows out of them. Then they pump the system.
When removing air on a car whose brake system has worked for more than 5 years, the fluid in the system is replaced with a new one.