BMW:: 5th E28/E34 series:: Pumping of hydraulic system of brakes

12:16. Pumping of hydraulic system of brakes

When pumping the brake system put on goggles. If liquid nevertheless gets to you into eyes, immediately wash out them water and see a doctor. The majority of types of brake fluid are flammable and can flare up at hit, for example, on hot details of the engine. Therefore with brake fluid it is necessary to handle not smaller care, than gasoline. Adding or replacing brake fluid, always use its recommended type and take it from just open container. Never reuse the liquid which remained when pumping system and do not add liquid in the tank, which a long time stood opened since it is potentially dangerous.

Brake fluid actively dissolves paint and plastic; if it was spilled, immediately wash away it a plentiful amount of water.

Pumping of hydraulic system is necessary to remove all air which could get to it during removal or installation of hoses, brake lines, a support or the main cylinder.

If air got to system because of lowering of the level of brake fluid, or as a result of a detachment of brake tubes from the main cylinder, then probably pumping of all four brake mechanisms will be required.

If the brake tube was disconnected only at a wheel, then pump over only a support or the wheel cylinder.

If the brake tube was disconnected in the socket located between the main cylinder and one of brake mechanisms, then it is necessary to pump over that part of system which is served by the disconnected tube.

When pumping all system entirely pump over it in such order: right back, left back, right forward, and at last, left forward brake mechanism.

PERFORMANCE ORDER

Remove residual vacuum from the vacuum amplifier, having pressed a brake pedal about 30 times at the switched-off engine. It will also take off pressure in system of anti-blocking of brakes where it is available.
Uncover the tank of the main cylinder and fill the tank with brake fluid. Establish a cover.

During the procedure of pumping as often as possible check the level of liquid and add liquid as necessary to prevent falling of its level below admissible when vials of air can get to the main cylinder.

For holding a procedure of pumping you need the assistant, an empty transparent plastic container and a piece of a transparent plastic or vinyl tube which can be got on pumping gates. It is also possible to use special set for pumping "without assistant". This set usually contains a tube or a bottle with the built-in unilateral valve - in this case the pedal will be normally squeezed out, but at its otpuskaniye air will back not get into system. When using the set "without assistant" follow the instructions attached to it; the same for sets for pumping under pressure. Anyway you will need also a reserve of fresh brake fluid of the recommended type and a wrench for work with the pumping gate.
Since the right back wheel, slightly release the pumping gate, then tighten it to situation when it is closed, but it can be easy and it is quickly open.

Put on one end of a tube the gate of pumping and ship other its end in a container with brake fluid.

Ask the assistant to squeeze out a brake pedal several times, and then to strong hold it squeezed out.

If the car is equipped with the ABS system, let the assistant will squeeze out a pedal not less than 12 times.

At the squeezed-out pedal of a brake open the pumping gate only so that the stream of liquid followed from a support or the wheel cylinder. Your assistant has to squeeze out softly a brake pedal up to the end and keep it in this situation. You watch how vials of air leave through the shipped end of a tube. When in couple of seconds the stream of liquid is slowed down, close the gate and ask the assistant to release a pedal.
Repeat the actions described in the previous two paragraphs until vials of air do not cease to leave their tubes, then tighten the gate of pumping and you pass to a back left wheel, then to forward right, and at last, to forward left, in such order, repeating a touch the procedure. Do not forget to check more often liquid level in the tank of the main cylinder.

Never use old brake fluid. It contains moisture which spoils components of the brake system.

At the end of all procedure fill the main cylinder with liquid.
Check operation of brake mechanisms. The squeezed-out pedal has to be motionless, not sink down. If necessary repeat all process. Do not use the car if you are not sure of serviceability of its brake system.