The clutch master cylinder generates the hydraulic pressure necessary to operate the clutch assembly. The clutch assembly has two key functions: to transmit power produced by the engine to the gearbox and to disrupt that power flow when the clutch pedal is depressed.
The clutch pedal is directly attached to the clutch master cylinder. When the clutch pedal is pressed, pressure generated by the clutch master cylinder applies pressure to the clutch slave cylinder. The clutch is then disengaged.
In order for the engine to operate efficiently, a range of gears is absolutely crucial. Power produced by the engine requires the clutch assembly-enabled interruption, which enables the vehicle to change gears and obtain neutral at a traffic light or stop sign.
If the clutch master cylinder or clutch slave cylinder fails, pressure will not be generated when the clutch pedal is pressed. When the driver tries to change gears, the pedal may stay on the floor, making it impossible to put the vehicle into gear.
To replace the clutch master cylinder, disconnect the clutch pedal from the clutch master cylinder. After accessing the clutch master cylinder—which can be very difficult—the hydraulic lines that carry the fluid to the clutch slave cylinder and the clutch master cylinder should be removed. Then, similar to the clutch fluid replacement procedure, the clutch fluid is bled. A new clutch master cylinder and hydraulic lines are installed and fresh fluid is added to the clutch fluid reservoir. Then, the clutch pedal is pressed and the pressure generated by the clutch master cylinder forces fresh fluid out to the clutch slave cylinder (which removes air from the system).