Hydraulic System Issues:
* Master Cylinder: This is the most likely culprit. A failing master cylinder can cause similar symptoms to a bad slave cylinder. It might be leaking internally, restricting fluid flow, or have a sticking piston. Inspect for leaks around the master cylinder.
* Hydraulic Lines and Hoses: Check all lines and hoses for kinks, blockages, or leaks. Even a small restriction can prevent proper fluid flow. Look carefully at the connections for leaks.
* Fluid Contamination: Air in the system can cause a spongy or sticking pedal. Proper bleeding is crucial after any work on the hydraulic system. Contaminated fluid (e.g., moisture) can also cause problems. Consider a complete fluid flush and refill.
* Residual Air in the System: Even with careful bleeding, some air might remain. Try bleeding the system again, ensuring you've followed the correct procedure for your vehicle.
* Pressure Plate/Clutch Disc Issues: Though less likely if the pedal was sticking before and you assumed a slave cylinder issue, a worn or damaged pressure plate or clutch disc could create drag and cause the pedal to stick.
Clutch Mechanism Issues (Independent of Hydraulics):
* Clutch Fork: The clutch fork connects the slave cylinder to the clutch throwout bearing. It could be bent, worn, or binding.
* Throwout Bearing: This bearing allows the pressure plate to disengage. If it's seized or damaged, it can cause the pedal to stick.
* Clutch Cable (if applicable): Some vehicles use a cable instead of a hydraulic system. If yours does, the cable might be frayed, stuck, or improperly adjusted.
Troubleshooting Steps:
1. Bleed the system thoroughly: This is the first step after replacing the slave cylinder. Make sure you follow the correct procedure for your vehicle (often involving opening a bleeder valve while pumping the clutch pedal).
2. Inspect the master cylinder: Check for leaks and see if the piston moves smoothly. A rebuild kit or replacement might be necessary.
3. Inspect the hydraulic lines and hoses: Look for leaks, kinks, or damage. Replace any suspect components.
4. Check for air in the system: If bleeding doesn't resolve the issue, there might be a persistent air leak somewhere in the system.
5. Inspect the clutch fork and throwout bearing: This usually requires removing the transmission bellhousing. A mechanic might be needed for this step.
6. Inspect the pressure plate and clutch disc (if accessible): Again, this often necessitates transmission removal.
If you're not comfortable working on your vehicle's clutch system, it's best to take it to a qualified mechanic. Improper repairs can lead to further damage. The diagnosis needs to systematically eliminate potential causes rather than simply replacing parts one by one.
