Ref 1 Replacing Brake Fluid

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Replacing brake fluid is divided into two steps.

Step 1: Replace brake fluid for the brake master cylinder circuit and clutch hydraulic system (conventional).

Step 2: Replace brake fluid for the booster circuit (brake booster and lock control). This requires activating the lock solenoids with a 9288 System Tester and removing the brake fluid from each lock cylinder.

Use of an electric filling and bleeding machine is recommended to guarantee fast and practical replacement of the brake fluid.

Pour new brake fluid in the supply tank until the level reaches the upper edge. Connect bleeder on the supply tank. Clamp the overflow hose (venting) with a hose clamp. Switch on bleeding machine.

A bottle must be used to catch the escaping brake fluid and therefore be able to check it for dirt and air bubbles as well as to determine the brake fluid consumption. Change volume for each wheel: approx. 250 cc. Bleed on both bleeder valves of each wheel.

Also drain about 50 to 100 cc of brake fluid on the bleeder valve of the clutch slave cylinder.

Switch off and disconnect the bleeding machine.

Remove hose clamp on the overflow hose (venting).


The rear underside trim panel must first be removed for the next step (booster circuit). If applicable for reasons of space, unscrew and also remove the engine splash guard. In addition, the battery should be in well .charged condition.

Connect System Tester 9288 in conjunction with connecting lead 9288/1 in the diagnostics socket in the passenger's foot-well (underneath a cover). Turn on ignition and tester. Select type of vehicle and PDAS system afterwards. Then go into the drive menu.




Carrera 4 Table Of Contents Carrera 2 Addendum Main Menu

03 Maintenance 911 Carrera 4

Select the bleeding position in the drive menu. Unscrew bleeder valve on the lateral lock cylinder and drain about 250 to 300 cc (max. 300 cc) of brake fluid after pressing the start key displayed in the tester.

Press stop key and tighten the bleeder valve.

Go into the pressure discharging position with the tester.


Pour in new brake fluid. Operate the brake pedal several times while the ignition remains turned on.

Afterwards activate the solenoids again with a 9288 System Tester (bleeding position in the drive menu) and drain about 200 cc of brake fluid on the bleeder valve of the axial lock cylinder.


Disconnect system tester.

Correct the brake fluid level. This requires operating the brake pedal first so many times (with the ignition on) until the pump assembly is operated. Correct the brake fluid level only after the pump assembly has been switched off. Never pour in so much brake fluid that the level is above the "max." mark.

03 - 34 Maintenance

Printed in Germany - III, 1989

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