Clutch Slave Cylinder Replacement and Bleeding – 2.5L NA

Overview

This guide outlines the procedure to replace the clutch slave cylinder and bleed the hydraulic system on a Porsche 944 (8-valve engine variants) for model years 1983–1985.5 (Pre-85.5) and 1986–1988 (85.5 Onwards). The clutch slave cylinder is critical for disengaging the clutch, and replacing a faulty unit restores proper clutch operation. Bleeding removes air from the hydraulic system to ensure smooth pedal feel. This guide is tailored for DIY enthusiasts with mechanical experience.

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Tools Required

• Metric wrench set (8mm to 19mm, 5/16 inch to 3/4 inch)
• Metric socket set (8mm to 19mm, 5/16 inch to 3/4 inch)
• Bucket
• Rags
• Mityvac hand vacuum pump (optional, for Bleeding Method 3)

Parts Required

• Clutch slave cylinder: 944 116 237 02
• DOT 4 brake fluid: 000 043 203 66

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.

Step 2: Remove the Old Slave Cylinder

2. Locate the clutch slave cylinder on the clutch housing, near the transmission.
3. Using a 13mm wrench, remove the two bolts securing the slave cylinder to the clutch housing. Keep the bolts for reinstallation.
4. Carefully slide the slave cylinder out of the clutch housing. Have a bucket and rags ready to catch any brake fluid that may drip.

Step 3: Install the New Slave Cylinder

5. Disconnect the fluid supply line from the old slave cylinder using a 13mm wrench.
6. Immediately connect the fluid supply line to the new clutch slave cylinder (944 116 237 02) to minimize fluid loss.
7. Choose a bleeding method from the options below (Methods 1, 2, or 3) to remove air from the hydraulic system. Follow the steps for your selected method before proceeding to Step 4.

Step 4: Bleed the Slave Cylinder

8. Bleed the slave cylinder using one of the following methods. Ensure the master cylinder reservoir remains full of DOT 4 brake fluid (000 043 203 66) during bleeding by checking the level frequently.

Bleeding Method 1 (Pre-Installation, One Person):

• Raise the rear of the vehicle at least 0.6 meters (2 feet) higher than the front using a jack and jack stands.

• Before installing the slave cylinder, hold it with the bleed nipple pointing upward.

• Open the bleed nipple using a 9mm wrench and manually push the slave cylinder’s operating shaft in and out to pump fluid through, expelling air. Have a bucket and rags ready to catch fluid.

• When no more bubbles appear, close the bleed nipple and tighten to 10 Nm (7 ft-lbs).

• Install the slave cylinder into the clutch housing and secure with the two bolts, tightening to 25 Nm (18 ft-lbs).

Bleeding Method 2 (Post-Installation, Two People):

• Install the slave cylinder into the clutch housing and secure with the two bolts, tightening to 25 Nm (18 ft-lbs).

• Raise the rear of the vehicle at least 0.6 meters (2 feet) higher than the front.

• Have an assistant press and hold the clutch pedal to the floor.

• Open the bleed nipple using a 9mm wrench to release fluid and air. Have a bucket and rags ready. Close the nipple when the flow stops.

• Have the assistant release the clutch pedal. If it stays on the floor, pull it up manually.

• Repeat the process (press pedal, open nipple, close nipple, release pedal) until the clutch pedal feels firm and operates normally.

Bleeding Method 3 (Post-Installation, Mityvac):

• Install the slave cylinder into the clutch housing and secure with the two bolts, tightening to 25 Nm (18 ft-lbs).

• Raise the rear of the vehicle at least 0.6 meters (2 feet) higher than the front.

• Connect a Mityvac hand vacuum pump to the bleed nipple.

• Open the bleed nipple and use the Mityvac to draw fluid through until it flows clear with no bubbles. Ensure the reservoir stays full.

• Close the bleed nipple and tighten to 10 Nm (7 ft-lbs).

• Slowly pull the clutch pedal off the floor to draw fluid into the master cylinder. Check the reservoir level.

• Repeat the vacuum process if the pedal feels spongy, then pump the pedal several times to confirm normal operation.

Step 5: Reinstall the Starter

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

Post Procedure Checklist

• Check the clutch pedal for firm, normal operation with no sponginess.
• Inspect the slave cylinder and fluid line connections for leaks.
• Ensure the master cylinder reservoir is filled to the proper level with DOT 4 brake fluid (000 043 203 66).
• Test drive the vehicle for 5 miles (8 km) to confirm smooth clutch engagement and disengagement.

Sources

• Clark’s Garage
• Pelican Parts Technical Articles
• Porsche 944 Workshop Manual