Clutch Slave Cylinder Replacement and Bleeding

Overview

This guide walks you through replacing the clutch slave cylinder and bleeding it on your Porsche 944 S / S2 with a 16v engine. The replacement itself is straightforward, but bleeding the system to remove air can be tricky. A properly functioning slave cylinder is crucial for smooth clutch operation, so this procedure ensures your clutch pedal works as it should.

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Tools Required

• Metric wrench set (sizes including 13mm wrench for bolts)
• Metric socket set
• Bucket (for catching brake fluid)
• Rags
• Mityvac hand vacuum pump (optional, for Bleeding Method 3)

Parts Required

• Clutch slave cylinder for Porsche 944 S / S2, 944 116 237 03
• DOT 4 brake fluid

Required Additional Procedures

Steps in these procedures are required to complete this process:

• Starter Removal and Installation

Step-by-Step Procedure

Step 1: Remove the Starter

1. Follow this link to ensure this step – Starter Removal and Installation – of the process is followed accurately. This provides access to the clutch slave cylinder on the Porsche 944 S / S2.

Step 2: Remove the Old Slave Cylinder

2. Locate the two retaining bolts securing the slave cylinder to the clutch housing. Using a 13mm wrench, remove these bolts.
3. Carefully slide the slave cylinder out of the clutch housing. Have a bucket and rags ready to catch any brake fluid that may spill.

Step 3: Prepare and Install the New Slave Cylinder

4. Have your new slave cylinder (944 116 237 03) ready. Disconnect the fluid supply line from the old slave cylinder and quickly connect it to the new one to minimize fluid loss.
5. Choose one of the bleeding methods below (Method 1, 2, or 3) to remove air from the system before or after installation, as noted.

Step 4: Bleed the Slave Cylinder

6. Bleeding Method 1 (Pre-Installation – One Person Job):
   • Raise the rear of the vehicle at least 2 feet (0.6 meters) higher than the front using a jack and jack stands.
   • Hold the new slave cylinder with the bleed nipple pointing up as high as possible.
   • Open the bleed nipple with a 10mm (3/8 inch) wrench. Push the operating shaft in and out like a pump to force air out. Catch fluid with rags and a bucket.
   • Close the nipple when no more bubbles appear. Tighten to 10 Nm (7 ft-lbs).
   • Slide the slave cylinder into the clutch housing and secure it with the two bolts, tightening to 20 Nm (15 ft-lbs).
7. Bleeding Method 2 (Post-Installation – Two Person Job):
   • Install the slave cylinder into the clutch housing and tighten the bolts to 20 Nm (15 ft-lbs).
   • Raise the rear of the vehicle at least 2 feet (0.6 meters) higher than the front.
   • Have an assistant press the clutch pedal to the floor and hold it.
   • Open the bleed nipple with a 10mm (3/8 inch) wrench. Catch fluid with a bucket and rags. Close it when fluid stops flowing.
   • Have your assistant release the pedal (pull it up manually if needed the first few times). Repeat until the pedal feels firm.
8. Bleeding Method 3 (Post-Installation with Vacuum Pump – Two Person Job):
   • Install the slave cylinder into the clutch housing and tighten the bolts to 20 Nm (15 ft-lbs).
   • Raise the rear of the vehicle at least 2 feet (0.6 meters) higher than the front.
   • Have an assistant press the clutch pedal to the floor—it should stay down.
   • Connect a Mityvac pump to the bleed nipple. Open the nipple with a 10mm (3/8 inch) wrench and draw fluid until it’s clear with no bubbles. Close the nipple and tighten to 10 Nm (7 ft-lbs).
   • Slowly pull the pedal up by hand to draw fluid into the master cylinder. Repeat if the pedal feels spongy.

Step 5: Check the Master Cylinder Reservoir

7. Throughout bleeding, frequently check the master cylinder reservoir under the hood. Keep it full with DOT 4 brake fluid to prevent air from entering the system.

Step 6: Reinstall the Starter

8. Follow this link to ensure this step – Starter Removal and Installation – of the process is followed accurately to reinstall the starter.

Post Procedure Checklist

• Check for leaks around the slave cylinder and fluid line connections.
• Pump the clutch pedal 5-10 times. It should feel firm, not spongy.
• Ensure the clutch engages and disengages smoothly when shifting gears.
• Verify the master cylinder reservoir is topped off with DOT 4 brake fluid.

Sources

1. Clark’s Garage
2. Porsche 944 (Workshop Manual, Volume 4)