Brakes – Master Cylinder Replacement – 2.5L NA

Overview

This procedure outlines how to replace the brake master cylinder on all Porsche 944 variants with an 8-valve engine configuration. The master cylinder is a critical component that pressurizes brake fluid to engage the brakes. Replacing it ensures proper braking performance and safety. This guide covers both pre-1985.5 (1983–1985.5) and 1985.5 onwards (1986–1988) variants, noting specific differences where applicable.

Pink and blue text represent links to additional resources, tools, parts, and partner websites.

Tools Required

• Metric wrench set (including 13mm (1/2 inch) and 15mm (9/16 inch) wrenches)
• Catch rags
• Hand vacuum pump

Parts Required

• Master Cylinder (Pre-1985.5): 944 355 011 00 (Girling) or 944 355 011 01 (ATE)
• Master Cylinder (1985.5 Onwards): 944 355 011 00 (Girling) or 944 355 011 01 (ATE)
• O-Ring (between Master Cylinder and Brake Booster): 211 611 243
• Grommet for Reservoir to Master Cylinder (Pre-1985.5): 211 611 817 A
• Grommet for Reservoir to Master Cylinder (1985.5 Onwards): 911 355 922 00

Step-by-Step Procedure

Step 1: Prepare the Work Area

1. Place catch rags under the brake master cylinder to protect painted surfaces from brake fluid spills. Brake fluid can damage paint, so act quickly to clean any spills.

Step 2: Drain the Brake Fluid Reservoir

2. Use a hand vacuum pump to remove as much brake fluid as possible from the reservoir. This step is optional but reduces mess during removal.

Step 3: Remove the Brake Fluid Reservoir

3. Pull the reservoir straight up to detach it from the master cylinder. If it’s stuck, gently rock it back and forth to free it from the rubber grommets (211 611 817 A for Pre-1985.5 or 911 355 922 00 for 1985.5 Onwards).
4. Place the reservoir on the fender well, keeping the slave cylinder line and level sensor wires attached. Place rags underneath to catch any dripping fluid.

Step 4: Remove the Master Cylinder

5. Locate the two retaining nuts securing the master cylinder to the brake booster. Use a 13mm (1/2 inch) wrench to remove these nuts.
6. Carefully pull the master cylinder away from the brake booster and remove it from the vehicle. Ensure the O-ring (211 611 243) between the master cylinder and brake booster is not lost, as it will be reused or replaced.

Step 5: Prepare the New Master Cylinder

7. Follow the instructions provided with the new master cylinder (944 355 011 00 or 944 355 011 01) to fill it with brake fluid before installation. Typically, this involves:

– Installing the reservoir onto the new master cylinder with the appropriate grommets (211 611 817 A for Pre-1985.5 or 911 355 922 00 for 1985.5 Onwards).

– Attaching nipples to the brake line ports with clear tubing routed back to the reservoir.

– Filling the reservoir with fresh brake fluid.

– Pressing the master cylinder piston to circulate fluid through the tubing until no bubbles appear.

Step 6: Install the New Master Cylinder

8. Position the new master cylinder onto the brake booster, ensuring the O-ring (211 611 243) is in place.
9. Secure the master cylinder with the two retaining nuts, tightening them to 25 Nm (18 ft-lbs) using a 13mm (1/2 inch) wrench.
10. Reattach the brake lines to the master cylinder ports, tightening the fittings to 15 Nm (11 ft-lbs) using a 15mm (9/16 inch) wrench.

Step 7: Bleed the Brake and Clutch Systems

11. Bleed the brake system to remove air bubbles. Follow this link to ensure this step – Brake System Bleeding – is followed accurately.
12. Bleed the clutch system, as the master cylinder shares fluid with the clutch. Follow this link to ensure this step – Clutch System Bleeding – is followed accurately.

Post Procedure Checklist

• Check for brake fluid leaks at the master cylinder, brake lines, and reservoir connections.
• Test the brake pedal for firmness and ensure it does not sink when held.
• Verify the clutch pedal operates smoothly and engages correctly.
• Confirm the brakes engage properly by pressing the pedal and checking for responsiveness.
• Inspect the reservoir fluid level and top off with fresh brake fluid if necessary.

Sources

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