Clutch Master Cylinder
A clutch master cylinder uses a single piston and seals like a brake master cylinder to force hydraulic fluid through the line and on to the slave cylinder. They can develop leaks both internally and externally. If there is a loss of pressure after the clutch is applied there may be an internal leak. Also check for an external leak inside of the vehicle on the floor board, behind the clutch pedal.
Clutch master cylinder symptoms include a hard brake pedal. A hard pedal may be the result of the piston binding in the master cylinder bore. Another thing that can cause a hard pedal is a blocked compensation port. This is usually caused by improper adjustment of the clutch pedal.
When a leak or binding occurs it will be necessary to rebuild or replace the master cylinder. Rebuilding kits are available for most clutch master cylinders. If it's a cast iron cylinder it should be honed and cleaned with brake fluid before replacing the internal parts. The aluminum masters should be completely cleaned with brake fluid but not honed before installation. This is because the hone will remove the coating used to seal and harden the aluminum bore.
