To troubleshoot the slave cylinder for a clutch, check for fluid leaks and air inside the lines, depress the clutch pedal to check if the clutch is able to release, and check to see if dirt and grime have accumulated on the slave cylinder. Bleed the slave cylinder to resolve the issues, or replace the part.
Fluid leakage and presence of air inside the lines occurs when the seal of the slave cylinder of a clutch gets damaged. This reduces the pressure in the system and leads to a soft clutch pedal.
When the pedal of the clutch is depressed completely and the clutch can't release, the clutch is stuck. This can occur due to leakage or a defect in the slave cylinder. In such a case, it is not possible to shift the transmission and grinding of the gears occurs. Also, the slave cylinder may not be able to shift the throw out bearing.
If the slave cylinder is leaking, bleed it. If this does not resolve the issue, replace the part.
If the slave cylinder is unable to release the pedal of the clutch, look for accumulated sediment on the cylinder. If the vehicle is an old one, look for dirt on the hydraulic linkage's lowest portion. To resolve this issue, flush the linkage or replace the slave cylinder.