Brakes – Master Cylinder Replacement

Overview

This procedure walks you through replacing the brake master cylinder on a Porsche 944 with it a 16v engine (1989-1991). The master cylinder pressurizes brake fluid for both the brakes and hydraulic clutch, making it essential for safe operation. Replace it if you notice leaks, soft brakes, or clutch issues.

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Tools Required

• Metric wrench set (including 13mm wrench for retaining nuts)
• Catch rags
• Hand vacuum pump

Parts Required

• Master cylinder (944 355 011 10 for Girling or 944 355 011 01 for ATE, specific to 944, 1989-91)
• O-ring between master cylinder and brake booster (211 611 243)
• Grommet for reservoir to master cylinder (911 355 922 00)

Required Additional Procedures

Steps in these procedures are required to complete this process:

• Brake Fluid Replacement and Bleeding

Step-by-Step Procedure

Step 1: Prepare the Work Area

1. Place catch rags under the brake master cylinder to catch any brake fluid spills. Keep fluid off painted surfaces to avoid damage.
2. (Optional but recommended) Use a hand vacuum pump to drain as much brake fluid as possible from the reservoir. This minimizes mess during removal.

Step 2: Remove the Reservoir

3. Pull the brake fluid reservoir straight up to detach it from the master cylinder. Gently rock it if needed to free it from the rubber grommets (911 355 922 00).
4. Use catch rags to catch any fluid that drips from the reservoir.
5. Set the reservoir aside on the fender well, keeping the slave cylinder line and level sensor wires attached. Place rags underneath to catch residual fluid.

Step 3: Remove the Master Cylinder

6. Use a 13mm wrench to remove the two retaining nuts holding the master cylinder to the brake booster.
7. Carefully pull the master cylinder off the brake booster and remove it from the car.

Step 4: Prepare the New Master Cylinder

8. Follow the instructions with your new master cylinder (944 355 011 10 or 944 355 011 01). Typically, attach the reservoir (911 355 922 00) and install nipples with clear tubing into the brake line ports, routing the tubing back to the reservoir.
9. Fill the reservoir with fresh brake fluid.
10. Press the master cylinder piston to push fluid through the tubing until no bubbles appear.

Step 5: Install the New Master Cylinder

11. Position the new master cylinder onto the brake booster, ensuring the O-ring (211 611 243) is seated properly.
12. Secure it with the two retaining nuts using a 13mm wrench. Tighten to 23 Nm (17 ft-lbs).
13. Reattach the brake lines to the master cylinder ports.

Step 6: Finalize the Installation

14. Follow this link to ensure this step – Brake Fluid Replacement and Bleeding – of the process is followed accurately.

Post Procedure Checklist

• Check for brake fluid leaks around the master cylinder and brake lines.
• Test the brake pedal for a firm, responsive feel.
• Test the clutch pedal to ensure smooth operation.

Sources

• Clark’s Garage
• Pelican Parts
• Porsche 944 Workshop Manual, Volume 1
• Youtube