There are many causes of a heavy clutch pedal; one of the most common causes is a worn out clutch. When the clutch is starting to wear out, it does not spin at the same speed as the flywheel. This creates friction, which requires pushing harder on the clutch pedal to change gears. There are also a few other auto parts that cause a heavy clutch pedal.
When a clutch cable does not have the right amount of tension to move the pedal, the pedal can be hard to push. The clutch cable is most often damaged after an accident or after a car has gone over a bump at high speeds. The cable does not often wear out or become bent from normal driving. Another possible cause of a heavy clutch pedal is a malfunctioning clutch cylinder. The cylinder is responsible for building the necessary amount of pressure to change gears. A malfunctioning clutch cylinder causes the clutch pedal to be heavy.
It is also possible that the clutch simply needs to be adjusted. If a new clutch has recently been installed, this is likely the reason the clutch pedal is heavy. It is best to look into this possibility first, since it is a very easy fix.