Clutch Master Cylinder Replacement

Overview

This guide walks you through replacing the clutch master cylinder on a Porsche 944 S / S2 with a 16v engine (1990-91 models). The clutch master cylinder is a key part of the hydraulic system that helps you press the clutch pedal smoothly. Replacing it ensures proper clutch operation, preventing issues like a spongy pedal or difficulty shifting gears.

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

Tools Required

• Work light
• 10mm (3/8 inch) socket
• 13mm (1/2 inch) socket
• Socket wrench with extensions and universal adapter
• Needle nose pliers
• Slip joint pliers
• 12mm flare nut wrench
• Rags
• Ziploc bags
• Motive pressure bleeder or clear plastic tube and a helper
• Catch pan
• 7mm wrench
• 13mm box/open wrench
• Turkey baster
• Hydraulic jack
• Jack stands
• Side cutters

Parts Required

• Clutch Master Cylinder 944-423-149-00
• Gasket 928-423-191-00
• Bushing / Slide Bearing 999-924-039-00
• Blue Brake Reservoir Hose (approximately 2 feet)
• Stainless Hose Clamps
• Brake Fluid (ATE Super Blue recommended, 1 quart)

Required Additional Procedures

Steps in these procedures are required to complete this process:

• Clutch Slave Cylinder Bleeding

Step-by-Step Procedure

Step 1: Prepare the Car

1. Lift the front of your Porsche 944 S / S2 using a hydraulic jack and secure it on jack stands. This gives you room to work under the car and access the clutch slave cylinder later for bleeding.

Step 2: Remove the Pedal Cluster Cover

2. Get under the dashboard near the clutch pedal. Find the plastic cover over the clutch master cylinder’s connecting rod.
3. Use a 10mm (3/8 inch) socket to remove the three nylon nuts holding the cover (two on the left edge, one on the right rear corner, as seen from behind the car looking forward).
4. Pull the cover off and set it aside with the nuts in a Ziploc bag.

Step 3: Disconnect the Push Rod from the Clutch Pedal

5. Locate the spring clip holding the clevis to the clutch pedal. Use needle nose pliers to pull the clip downward and remove it.
6. Mark the spot where the clevis meets the push rod with a paint pen or nail polish for reinstallation reference.
7. Push the clevis bolt (a beefy bolt on the 944 S / S2) out to the right side (your left as you face it). The push rod and clevis should now be free from the pedal.
8. Keep the plastic bushing, spring clip, and bolt in a Ziploc bag. Replace the bushing 999-924-039-00 if it’s damaged.

Step 4: Drain the Brake Fluid Reservoir

9. Place rags around the brake fluid reservoir to catch spills and protect your paint.
10. Use a turkey baster to suck out most of the brake fluid from the reservoir.

Step 5: Disconnect the Fluid Lines

11. Loosen the hose clamp on the blue brake fluid hose at the reservoir with a 13mm (1/2 inch) wrench or side cutters if it’s a factory clamp. Carefully pull the hose off the reservoir nipple.
12. Use a 12mm flare nut wrench to loosen and remove the solid brake line from the front of the clutch master cylinder. Move the line aside.

Step 6: Remove the Clutch Master Cylinder

13. Use a 13mm (1/2 inch) socket with a universal adapter to remove the two bolts securing the clutch master cylinder to the firewall. Keep rags below to catch any falling parts.

14. Check the gasket 928-423-191-00. Replace it if torn.

15. With slip joint pliers, gently pull the master cylinder away from the firewall, then angle it upward to remove it fully, including the boot, push rod, and clevis.

Step 7: Prepare the New Clutch Master Cylinder

16. Unbox the new clutch master cylinder 944-423-149-00 and remove the plastic cap from the front threads.
17. Take the clevis and stop nut off the old push rod and attach them to the new one.
18. Adjust the push rod length to 147.0 mm (5.79 inches) for left-hand drive (LHD) cars or 109.5 mm (4.31 inches) for right-hand drive (RHD) cars, adding 3 mm (0.12 inches) to account for the firewall thickness. Lock it with the stop nut.
19. Cut 16-18 inches (40-45 cm) of new blue brake hose and attach it to the master cylinder’s angle pipe with a stainless hose clamp. Don’t overtighten. Add a second clamp loosely for now.

Step 8: Install the New Clutch Master Cylinder

20. Position the new master cylinder and hose against the firewall gasket. Have a helper guide the push rod toward the clutch pedal.

21. Tighten the two 13mm bolts with concave washers to secure it to the firewall. Torque to 23 Nm (17 ft-lbs).

22. Reattach the solid brake line to the front of the master cylinder using a 12mm flare nut wrench.

23. Connect the blue hose to the brake fluid reservoir nipple and tighten the stainless clamp carefully.

Step 9: Reconnect the Push Rod to the Clutch Pedal

24. Under the dash, slide the clevis bolt through the pedal and clevis, then add the bushing 999-924-039-00 and spring clip.
25. Check for about 1/8 inch (3 mm) of free play before the clutch engages. Adjust the push rod if needed after bleeding.

Step 10: Bleed the Clutch System

26. Fill the brake fluid reservoir above the minimum line with fresh brake fluid.
27. Attach a Motive pressure bleeder to the reservoir, pressurize to 10-15 psi (0.7-1 bar), and check for leaks. Fix any before proceeding.
28. Add 1 quart (0.95 liters) of brake fluid to the bleeder and pump to 15 psi (1 bar).
29. Slide under the car with a catch pan, 7mm wrench, and clear tubing. Open the bleed nipple on the clutch slave cylinder until fluid runs clear with no bubbles, then close it. Follow this link to ensure this step – Clutch Slave Cylinder Bleeding – is followed accurately.
30. Clean up any spills.

Step 11: Finalize and Test

31. Remove any rags from the work area.
32. Press the clutch pedal. It should feel firm and spring back fully.
33. Lower the car off the jack stands.
34. Test drive the car for 5 miles (8 km) to confirm smooth clutch operation.

Post Procedure Checklist

• Check for leaks at the clutch master cylinder and reservoir connections.
• Ensure the clutch pedal has 1/8 inch (3 mm) of free play and feels firm.
• Verify smooth gear shifting during the test drive.

Sources

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