Reverse bleeding a clutch is a technique used to remove air bubbles from a hydraulic clutch system by injecting brake fluid from the bleeder valve at the slave cylinder up to the master cylinder. This method is often preferred as air naturally rises, making it easier to expel from the system. This guide will focus on reverse bleeding a clutch in a Porsche 993.
Understanding Reverse Bleeding and its Benefits
Traditional bleeding methods involve pumping the clutch pedal and opening the bleeder valve to force fluid and air out. However, stubborn air pockets can sometimes remain, leading to a spongy pedal feel and poor clutch engagement. Reverse bleeding addresses this issue by directly introducing fluid at the lowest point of the system, effectively pushing air upwards and out of the master cylinder reservoir.
Reverse Bleeding a Porsche 993 Clutch: Step-by-Step
While some argue that pressure bleeding is sufficient for a 993, reverse bleeding can offer a more thorough solution for stubborn air in the system. Here’s how to perform a reverse bleed:
Materials Needed:
- Brake fluid (DOT 4 approved for your Porsche 993)
- Clear tubing that fits snugly over the bleeder valve
- Syringe or oil can with a fitting for the bleeder valve
- A container to catch the old fluid
- Wrench for the bleeder valve
- Rags or shop towels
Procedure:
- Prepare the Vehicle: Park the car on a level surface and engage the parking brake.
- Locate the Bleeder Valve: The bleeder valve is typically located on the slave cylinder, near the transmission.
- Connect the Tubing: Attach the clear tubing to the bleeder valve and submerge the other end in the container for collecting old fluid.
- Fill the Syringe/Oil Can: Fill the syringe or oil can with fresh brake fluid. Ensure there are no air bubbles in the syringe or oil can.
- Inject Fluid: Connect the syringe or oil can to the tubing on the bleeder valve and slowly inject fluid into the system. You should see air bubbles rising in the master cylinder reservoir.
- Monitor the Reservoir: Keep an eye on the fluid level in the master cylinder reservoir and top it off as needed to prevent introducing more air.
- Repeat as Necessary: Continue injecting fluid until no more air bubbles emerge from the reservoir.
- Close the Bleeder Valve: Once all the air is out, tighten the bleeder valve.
- Test the Clutch: Start the car and test the clutch pedal feel. It should feel firm and engage smoothly. If the pedal still feels spongy, repeat the process.
Choosing the Right Tools for Reverse Bleeding
You can use a simple oil can or a more sophisticated tool like a Motive Power Bleeder for reverse bleeding. The Motive Power Bleeder pressurizes the system, allowing for a more controlled and efficient bleed.
Clutch Pedal Position During Bleeding a 993
Unlike some Porsche models (like the 986/987), the 993 clutch pedal should not be depressed during the bleeding process.
Conclusion: Mastering the Reverse Bleeding Technique
Reverse bleeding can be a highly effective method for achieving a firm and responsive clutch pedal in your Porsche 993. By understanding the process and using the right tools, you can confidently tackle this task and ensure optimal clutch performance. Remember to consult your vehicle’s service manual for specific instructions and torque specifications. A properly bled clutch system is crucial for smooth shifting and a pleasurable driving experience.
