If you drive a vehicle with a manual transmission, it has both a clutch master cylinder and a slave cylinder. When you press the clutch pedal, both cylinders work together so your transmission can safely shift. The master puts pressure on the slave, which extends its rod to push against a lever that disengages the clutch. There are two red flags for a bad clutch slave cylinder. First, your clutch pedal may begin to feel mushy or may go all the way to the floor and stay there. Second, you may notice brake fluid leaking out around the clutch. This indicates that the rubber seals inside the slave cylinder have broken. The fluid will be particularly dark and probably cloudy since broken seals also contaminate the brake fluid.