The clutch pedal is a lever that increases the amount of force you apply. When the clutch is pressed, the clutch master cylinder pushes fluid through the line, and into the slave cylinder on the other end. The slave cylinder pushes on the clutch fork, which disengages the clutch. When the clutch pedal is released, the clutch pushes the slave cylinder closed, forcing fluid back into the master cylinder, which lifts the clutch pedal and provides the force felt when pressing the clutch.

Low levels of clutch fluid or a need to top off the fluid are often signs of a problem with the clutch master cylinder.

The vehicle may become hard to shift if the clutch master cylinder is failing. It may need to be replaced.

If the clutch master cylinder fails, the clutch pedal may float to the floor when held, and the vehicle may attempt forward motion with the vehicle stopped and in gear. The clutch will attempt to engage as the fluid escapes compression in the master cylinder. In most cases, the clutch pedal will have little to no effect on the clutch.

Driving a vehicle without a working clutch is only possible if the transmission is shifted improperly, and push-started at every stop. While this may save a few dollars on wrecker services, it can cost the replacement of the manual transmission. It is better to have the vehicle towed, than risk further damage.

The clutch hydraulic system, including the clutch master cylinder, clutch slave cylinder, and fluid lines, will need replacement sometime during the serviceable life of most equipped vehicle's. They wear out with use, but this typically takes well over 100,000 miles of use. For vehicle's used in city driving, the system will require much more maintenance over the life of the vehicle. Changing the clutch fluid according to the manufacturer specified intervals may help prevent premature failure of these components.

Clutch master cylinder failure is most evident when the slave cylinder actuates properly, but pressure bleeds off while holding the clutch pedal. This means, that as the clutch pedal is held, the slave cylinder will slowly allow the clutch to engage, but is free of leaks, and in good condition. Normally, a leaking clutch master cylinder is a give-away. In most cases it is recommended to change the slave cylinder at the same time, as the master cylinder failing may be an indication of overall system condition. It is much more economical to replace both during the same service.

Replacing the clutch master cylinder requires that the fluid from the system is drained. Also, it is normally recommended to replace the clutch slave cylinder at the sale time. After draining the system of fluid, the slave cylinder and master cylinder will be removed from the vehicle by disconnecting the slave cylinder from the transmission bell housing, and removing the master cylinder from the firewall. The clutch hydraulic line should be removed with the slave cylinder and clutch master cylinder. Once separated from the vehicle, the new components will be fitted, and the line replaced if necessary. Installation is the reverse of removal, and once the system is in place, the system must be bled of air, and tested.

The clutch fluid should be flushed until clean and clear during this replacement.