Wet the sealing ring with brake fluid only.

Never use brake cylinder paste. Absolute cleanliness is essential. Use only non-fluffy cleaning cloths.

2. If there is an electrical fault at the pressure warning switch, always exchange the pump relay (R 51 / arrow) as well.


2. Evacuate all pressure from the system by pressing the brake pedal down about 25 times. The system is at zero pressure when the brake pedal feels hard as it is pressed.

3. Attach plug to pressure warning switch (arrow).


5. Connect pressure gauge SW 9509 to the pressure reservoir and check the switching points of the pressure warning switch and also for leakage in the booster circuit. The precise working proced. and desired values are stated on Page 47 - 9...47 -12 (Pressure tests on booster circuit).


If necessary, top up the brake fluid level at intervals so that the fluid reservoir is not drained completely. The booster circuit must be at zero pressure when connecting and removing the pressure gage.

4. Partly bleed the booster circuit as follows:

Open the bleed valve at the pressure reservoir. Attach the electrical plug to the pump. As soon as brake fluid emerges free from air bubbles, pull off the electrical plug and close the bleed valve. Next, charge the pressure reservoir completely. To do this, attach the electrical plug. As soon as the pump is heard to switch off, pull off the electrical plug and relieve the pressure completely at the pressure reservoir bleed valve. Slowly open the bleed valve and hold the bleed hose firmly. Warning: a pressure of up to 180 bar is present at the valve. Wear protective goggles and gloves.

6. After testing and assembly work has been completed, correct the brake fluid level (Page 47 - 4).

Do It Yourself Car Diagnosis

Do It Yourself Car Diagnosis

Don't pay hundreds of dollars to find out what is wrong with your car. This book is dedicated to helping the do it yourself home and independent technician understand and use OBD-II technology to diagnose and repair their own vehicles.

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