A clutch master cylinder contains a reservoir that stores the hydraulic fluid. It is connected to the clutch slave cylinder through hoses. When you push the clutch pedal, brake fluid flows from the clutch master cylinder to the slave cylinder, applying the pressure necessary to move (or engage) the clutch.
The clutch master cylinder has internal and external seals that can fail. If the external seals wear out, the clutch master cylinder will leak hydraulic fluid, reducing the amount of fluid in the car and causing the clutch to malfunction. You may also find leaked hydraulic fluid down by the clutch pedal (inside the car). If the internal seals wear out, the clutch fluid will continue to circulate inside instead of being directed to the slave cylinder. In that case, the clutch pedal will go all the way to the floor when you apply the clutch.
Symptoms that indicate you may need to replace the Clutch Master Cylinder & Slave Cylinder:
- Clutch pedal goes all the way to the floor.
- Clutch pedal does not return to position.
- Hydraulic fluid leaking around the clutch pedal.
- Not able to change gears.
Recommended best practice:
- Whenever the clutch master cylinder is replaced, it is recommended to replace the slave cylinder as well. When the master cylinder goes bad, it is extremely common for the slave cylinder to follow suit.
- Note that some clutch slave cylinders are installed inside the transmission. To replace this type of slave cylinder the transmission has to be removed.