Clutch problems fall into three categories:
a) The clutch does not release properly when the pedal is depressed, resulting in difficult engaging of gears.
b) Clutch slip, a condition where the engine speed increases when you give the car gas while in gear, but the car does not speed up accordingly.
c) Clutch judder, where the car does not take up smoothly as you let the clutch out.
Problem “a” is usually caused by faulty hydraulics. First, check that there is sufficient fluid in the clutch master cylinder. If the level is low, look for leaks at the master cylinder or slave cylinder, and rebuild or replace these cylinders as necessary. If the level is okay and there are no leaks evident, bleed the system to ensure there is no air present. Check that the flexible hose has not deteriorated; watch to see that it does not expand in diameter while a colleague pushes the clutch pedal. If the hydraulics are working properly, the end of the throwout fork arm should travel 3/8”. If the clutch does not release properly, even though the hydraulics are working correctly, either the throwout bearing is completely worn out (so the pressure plate is not being pushed far enough to release the disc), or the disc itself is hanging up. Either of these problems require that the engine be removed to inspect and remedy the situation.
Problems “b” and “c” both require that the engine be removed to get at the clutch. Clutch slip results from the disc being worn out or oily, (which also causes judder,) or the pressure plate springs being weak. Since getting to the clutch is such a labor intensive operation, we strongly recommend replacing the disc, pressure plate and throwout bearing if you have a mechanical problem with your clutch. Excess play of the lever will cause premature wear on the throwout bearing. A new throwout bearing has 11/64” of carbon thrust face exposed from the metal body; if yours has 1/8” or less, it should be replaced, too. If your disc has worn so far that the rivets are exposed, check the face of the flywheel for grooves, it must be removed and resurfaced if the surface is scored noticeably.
Special Note: While doing a clutch job, always check the ring gear for damage to the teeth, and install a new one if significant damage is present.