6.3.6. Removal of air from a hydraulic actuator

Pumping of brakes is necessary for removal of air from a hydraulic actuator which considerably reduces efficiency of the working brake system. Air can get to a hydraulic actuator owing to depressurization of system at repair or replacement of separate knots, and also when replacing brake fluid. Points the increased course of a pedal of a brake and its "softness" to availability of air in the drive of brakes.

It is not recommended to apply the liquid merged from system for filling of a tank as it is saturated with air, moisture and, perhaps, it is polluted.

Before removal of air from the brake system be convinced of tightness of all knots of the drive of brakes and their connections, clear a cover and a surface around a tank cover, fill a tank with brake fluid to a tag "MOVE". Then carefully clear unions for removal of air and remove from them protective caps.
Air from system is deleted at first from one contour, then from another, since wheel cylinders of back brakes.

Fig. 6.12. Removal of air from a hydraulic actuator of brakes: 1 – the union for pumping; 2 – hose; 3 – a vessel with liquid

Put on a head of the union 1 (fig. 6.12) a rubber hose 2 for liquid discharge, and lower its free end in a transparent vessel 3, partially filled liquid.
Having sharply pressed a pedal of a brake of 3-5 times with intervals 2–3 with, unscrew on 1/2–3/4 turns the union at the pressed pedal. Continuing to press a pedal, force out the liquid which is in system together with air through a hose in a vessel. After the pedal of a brake reaches forward extreme situation and the expiration of liquid through a hose will stop, wrap the union of production of air to the full. Repeat these operations until an exit of bubbles from a hose stops.
Holding a pedal in the pressed situation, wrap the union to the full and remove a hose. Wipe dry the union and put on a protective cap.
Repeat operations for other wheels, at first on the second wheel of the same contour, and then it is consecutive on both wheels of other contour.
During removal of air you monitor availability of liquid in a tank, without allowing an exposure of its bottom as at the same time air will get to system again.
At absence the pedal of a brake has to pass 1/2 full speeds in the drive of brakes of air.
To exclude influence of the vacuum amplifier on pumping of brakes, you carry out removal of air at the idle engine.
If in the hydraulic drive there is no brake fluid, then fill system as follows:
– fill in brake fluid in a tank of the main cylinder;
– unscrew on 1,5–2 turns unions on cylinders of all wheels;
– sharply pressing a pedal of a brake and smoothly releasing it, wrap unions in process of an effluence of liquid from them. Then pump over system.
During removal of air on the car which brake system worked long term replace the liquid which is in system new.