In an automobile equipped with a manual transmission, the clutch is the main link in the transfer of power from the engine to the transmission. Because the clutch is directly involved in this transmission of engine power, problems with the clutch are usually pronounced and easily noticeable. In many cases, problems such as pedal vibration provide a clue as to what is going wrong.
Misalignment occurs when the clutch assembly is not correctly aligned with the flywheel. This causes the clutch to engage unevenly, placing an unbalanced load on the clutch and flywheel surfaces. The usual result is chattering, pulsating and vibration of the clutch pedal.
Broken Diaphragm Spring
The diaphragm spring controls the amount of pressure applied to the pressure plate and clutch disc, and seats them against the flywheel. If the diaphragm spring is damaged or broken, this causes the clutch plate to engage the flywheel unevenly when applied or released, which in turn causes vibration and pulsation of the clutch pedal.
Warped Clutch Disc
The clutch disc is the portion of the clutch assembly that actually connects the flywheel to the transmission when you engage the clutch. It's made of a material similar to that of brake pads, and operates on the same principle of friction. In order to operate properly, all the contact surfaces of the clutch assembly must be smooth and flat, including the clutch disc. If the clutch disc becomes warped due to wear or overheating, it will not engage smoothly with the flywheel and pressure plate. This results in chattering, vibration and clutch pedal pulsation.
Improper Throw-Out Bearing Installation
The throw-out bearing is the part of the clutch assembly that engages and disengages the clutch. When you press the clutch pedal, the throw-out bearing moves forward and pushes on the pressure plate fingers, which releases the spring pressure and pushes the pressure plate against the clutch disc.
An improperly installed throw-out bearing will not contact the pressure plate fingers evenly or smoothly. This causes the pressure plate to push against the clutch disc unevenly, leading to vibration and pulsation of the clutch pedal.