With Hydraulic Brake Booster

Changing The Brake Fluid (hydraulic brake booster)

Important notes

Use only new DOT 4 brake fluid. Observe correct fluid change intervals and fluid grade.

Total brake fluid quantity for brake fluid change approx. 1.6 liters.


Brake fluid change procedure

Important notes

Depressurize booster circuit before changing the brake fluid.

Do not depressurize by actuating the brake pedal but rather at the bleeding valve of the pressure accumulator. This will allow part of the old brake fluid to be drained.





Caution: Start by filling the accumulator completely (with ignition key in position 1, actuate brake pedal until pump starts to run). After the pump has switched off, pull off electrical connector and release pressure completely from accumulator vent valve. Open bleeder valve slowly and keep bleeder hose in place.

Caution: A pressure of up to 180 bar is present in the system.
Wear goggles and protective gloves!

To allow the brake fluid to be changed in a rapid and practical manner, a filling and bleeding device should be used.

If the booster circuit has not been depressurized completely, do not actuate the brake pedal while the bleeder device is connected.


Changing the brake fluid: 1st step

With the booster circuit depressurized, top up with fresh brake fluid to upper edge of reservoir. Connect bleeder device to reservoir.

Clamp shut overflow hose/venting hose with a hose clamp. Note: The overflow hose/venting hose has been omitted as from October 1995. Switch on bleeder device. Bleeding pressure: approx. 1.5 bar.

- Use a recipient bottle to allow the escaping brake fluid to be checked accurately for cleanliness and freedom from bubbles and to determine the quantity of brake fluid used.

Fluid change quantity per wheel: approx. 250 cc.

Bleed at both bleeder valves on each wheel.

Caution: Pump the break pedal at least 10 times over its full travel after opening the first bleeder valve. This additional operation is only necessary for vehicles with hydraulic brake boosters and then only for the first bleeder valve.


Changing the brake fluid: 2nd step





- With the bleeder device switched on, drain approx. 200 cc brake fluid at pressure accumulator. For this purpose, connect electrical connector to pressurizing pump with ignition key in position 1. As soon as the specified quantity has been drained, pull off connector and close bleeder valve.

- Switch off and disconnect bleeder device. Remove hose clamp from overflow hose (vent).


- Fill pressure accumulator completely by connecting the electrical connector.





- After the pump unit has switched off, correct brake fluid level. Never top up beyond the "Max. mark".