Check for a stuck concentric slave cylinder.

Replace the concentric slave cylinder. Refer to Clutch Actuator Cylinder Replacement .

Check for improper return of clutch oil.

Perform the air bleeding. Refer to Hydraulic Clutch System Bleeding .

Check for a worn clutch disc or oil contamination.

Replace the necessary clutch components. Refer to Clutch Assembly Replacement : Diesel Engine  → 2.4 Engine .

Check for a warped pressure plate.

Replace the necessary clutch components.