Dunno much about cars but I was previously sent this by a mate:
CLUTCH SYMPTOMS
• Slipping — Slipping is usually an indication that the clutch disc and/or pressure plate have reached the end of the road. Most diaphragm clutches actually exert more force against the disc as it wears down, but older coil spring clutches do not. In some instances, though, slipping is caused by linkage that’s out of adjustment. The linkage is too tight and does not allow the release bearing to return to its normal rest position after the clutch pedal has been released. The same problem can occur if the linkage is binding. Another cause of slipping may be grease or oil on the clutch linings, flywheel or pressure plate.
• Chattering and Grabbing — If the clutch chatters or grabs instead of engaging smoothly, the most likely cause is oil or grease on the clutch linings. A leaky crankshaft rear main oil seal may be the source of the unwanted oil. There could also be a leaky transmission or transaxle input shaft seal, a manifold or valve cover oil leak on the engine, binding in the clutch linkage or a broken powertrain mount. Other causes of this condition include binding or rust on the input shaft splines, broken or damaged clutch facings or pressure plate assembly, a warped clutch disc, damaged or broken damper springs in the clutch disc hub, or a collapsed marcel spring in the clutch disc.
• Dragging and Disengagement Problems — If the gears grind when shifting or the clutch fails to completely disengage when the pedal is depressed all the way to the floor, the clutch disc may be dragging against the flywheel or pressure plate. The most likely causes here would be insufficient linkage travel (check the adjustment), a damaged clutch disc (loose or warped friction linings, or a damaged or bent hub), a broken release lever on a coil spring clutch cover, binding or rust on the input shaft or a broken powertrain mount.
If you suspect the clutch disc is dragging, try this test: with the engine and transmission at normal temperature, push the clutch pedal all the way to the floor, wait five or six seconds, then shift the transaxle into reverse. If the transaxle does not shift smoothly, the clutch disc is dragging.
If the clutch fails to release at all, and there is less than the normal resistance in the pedal, the clutch cable or release fork may be broken or a linkage rod may have become disconnected. If the car has a hydraulic linkage, the fluid level in the master cylinder may be low, the piston seal in either the master or slave cylinder may have failed, or the fluid hose may be leaking. If pedal effort, free play and travel are normal, but the clutch fails to release, the clutch disc or pressure plate assembly may be damaged.
If the clutch was just replaced, the clutch disc may have been installed backwards with the wrong side facing the flywheel bolts and disc hub. Using extra washers or lock washers under the bolts may raise the bolt heads, causing them to make contact with the disc hub. Another possibility is mismatched components. Installed height is especially critical with front-wheel-drive diaphragm clutches for proper operation. If a clutch disc from one manufacturer is used with a pressure plate assembly from a different manufacturer, or the release bearing is not the correct one for the application, the release bearing may not push the clutch fingers in far enough to disengage the clutch.
• Pedal Pulsation — If the clutch pedal pulsates or vibrates when depressed, it usually indicates misalignment between the engine and transaxle or an internal clutch problem, such as a broken clutch diaphragm spring, a warped or misaligned pressure plate, or a warped or bent clutch disc.
• Clutch Noise — The conditions under which a noise is heard will help diagnose the source of the problem. If the noise only occurs when the clutch pedal is depressed, the most likely cause would be a faulty release bearing. On applications where the release bearing is in light contact with the clutch fingers all the time, the bearing may be noisy all the time or only when pressure against it increases.
Clutch noise that occurs only while the clutch is engaged (pedal up) may indicate excessive play between the splines on the clutch disc hub and input shaft, a damaged center damper in the clutch disc hub or misalignment between the engine and transaxle.