Any hydraulic system works normally if air is removed from it.
During removal of air add only pure DOT 3 liquid recommended by the manufacturer.
Never reuse liquid which flowed out from the hydraulic drive of coupling.
Brake fluid is hygroscopic, that is absorbs moisture from air. Therefore liquid, stored a long time in open ware, is not recommended to use.
At continuous leak of liquid from the hydraulic drive or hit in hydraulic system of air define the reason and the place of leak and eliminate damage.
You make removal of air from the hydraulic drive of coupling as follows (in the course of pumping you watch that the level of brake fluid did not fall below the middle of a tank of the brake system):
Remove a protective cap from the pumping union on the working cylinder of coupling and clear the union.
Put on one end of a transparent hose the pumping union, lower the second end of a hose in the glass vessel filled with brake fluid on 5–7 cm.
The assistant has to press a coupling pedal, and at the pressed pedal unscrew the pumping union on a half of a turn.
Continuing to press a pedal, force out the liquid which is in system together with air through a hose in capacity. After the pedal reaches extreme lower situation and the liquid effluence through a hose will stop, screw the pumping union to the full.
Repeat these operations, the air outlet from a hose will not stop yet.
Holding a pedal in the pressed situation, tighten the pumping union against the stop and remove a hose from the pumping union.
Wipe the union of pumping and establish a protective cap.