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12.2. Pumping of the hydraulic brake system

Pumping union arrangement on a forward support

 The union of pumping is specified by an arrow.

Pumping union arrangement on the back working brake cylinder

 The union of pumping is specified by an arrow.

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

At absence in system of brakes of air, the pedal has to pass about a half of the course. To exclude influence of the vacuum amplifier on pumping of brakes, to make removal of air at the idle engine.

PERFORMANCE ORDER
1. Before removal of air to check tightness of all knots of the drive of brakes and their connections.
2. To remove a dustproof cap from the union of pumping of the wheel cylinder, to clear it and to dress on it a pure transparent hose which other end to lower in the capacity which is partially filled with brake fluid. Capacity has to be at least 300 mm above the pumping union. Thanks to it hit of air in the cylinder through a pumping union carving is prevented.
3. To press sharply a pedal of a brake of 3-5 times with an interval 2–3 sec., to unscrew half way the pumping union at the pressed pedal.
4. Continuing to press a pedal, to force out the liquid which is in system together with air through a hose in capacity.
5. After the pedal reaches extreme forward situation, and the liquid effluence through a hose will stop, to screw the pumping union to the full.
6. The air outlet from a hose will not stop repeating these operations yet.
7. Holding a pedal in the pressed situation, to screw up the pumping union against the stop and to remove a hose.
8. To wipe the union of pumping and to establish a protective cap.
9. To repeat these operations for other wheels.
Prevention

During removal of air it is constant to monitor availability of brake fluid in a tank, without allowing an exposure of its bottom since at the same time air will get to system again.

Sequence of pumping

ORDINARY BRAKE SYSTEM

1) Right back wheel.
2) Left forward wheel.
3) Left back wheel.
4) Right forward wheel.

C ABS BENDIX SYSTEM

Detachment of the three-contact socket when pumping the Bendix system with ABS

Before performance of pumping to switch off ignition and to disconnect the brown three-contact socket from hydraulic assembly of the modulator.

Arrangement on the hydraulic modulator of the main and additional union of pumping of the Bendix system with ABS

1 – main union of pumping,

2 – additional union of pumping

1) Back brake, the most remote from the main cylinder.
2) Back brake, the closest to the main cylinder.
3) Forward brake, the most remote from the main cylinder.
4) Forward brake, the closest to the main cylinder.
5) Hydraulic modulator.

BOSCH C ABS SYSTEM

1) Left forward wheel.
2) Right forward wheel.
3) Left back wheel.
4) Right back wheel.

If there are difficulties when pumping the hydraulic Bosch system with ABS, to execute pumping in the following order:

1) Right back brake.
2) Left back brake.
3) Left forward brake.
4) Right forward brake.