20.2. Pumping of brakes


We perform work together with the assistant on a viewing ditch or the elevator.

Pumping of brakes is necessary when replacing brake fluid, and also for removal of the air which got to a hydraulic actuator at repair or replacement of separate knots of the brake system.
Air is deleted at first from one contour of system, then from another. We begin pumping with the right back wheel cylinder.

We remove a cap from the flowing union of the back brake cylinder.

We put on a transparent hose the union, having lowered its free end in a vessel.

The assistant presses a brake pedal three-four times with an interval one-two seconds and holds a pedal of pressed. A key "on 8" we unscrew the pumping union on 1/2–3/4 turns. At the same time a part of brake fluid and air are forced out in a vessel, and the pedal falls to a floor. Vials of air are well visible in a transparent hose. We wrap the union of pumping and we repeat this operation until an exit of vials of air completely does not stop.
During removal of air from system we watch liquid level in a tank of the main brake cylinder and if necessary we add it.
Similarly we pump over the left back wheel cylinder. Then we delete air from the top unions of the left and right blocks of cylinders of forward wheels.

We remove a cap of the top union of the block of brake cylinders of a forward wheel (for descriptive reasons the wheel is removed).

We pump over forward brake cylinders of one contour.

For pumping of other contour we delete air from the lower unions of blocks of cylinders of forward wheels in any order.

We remove a cap from the lower union of the block of brake cylinders of a forward wheel.

We pump over other contour.

In the absence of air in system the brake pedal has to be "rigid", i.e. when pressing to pass no more than a half of distance to a floor.