Symptoms of a Bad Slave Cylinder

by Katina Blue
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A vehicle's slave cylinder -- part of the hydraulic clutch system located on the outside or inside of the transmission -- is a device which aids in clutch disengagement. When a clutch pedal is pressed, the master cylinder applies pressure to the slave cylinder, causing the clutch to release. If the slave cylinder is faulty, the clutch will malfunction, preventing a vehicle from properly shifting gears. Several symptoms are indicative of a slave cylinder problem.

Loose Pedal

The way a clutch pedal feels when pressed will often indicate if a slave cylinder is faulty. The clutch might feel loose or soft and may not shift into action, even when the pedal is pressed completely to the floor. This occurs when a seal inside the slave cylinder starts leaking, allowing air to seep in.

Low Fluid Levels

Monitoring clutch fluid levels may help with diagnosing a bad slave cylinder. If a slave cylinder is leaking, clutch fluid levels are quickly depleted and need frequent refills. If the clutch fluid is below the normal level immediately after a refill, or within a short time, check the cylinder for cracks or holes that might allow seepage.


Fluid leaking from a slave cylinder indicates a problem. Internal leaks are the most common and are diagnosed by examining the cylinder. Sometimes cracks in the cylinder are not visiblem and squeezing the bottom part of it, called the boot, will help reveal any weak spots on the surface. Also, look for spilled fluid -- medium to dark red in color -- on the ground below the slave cylinder. Leaking from a master cylinder can produce symptoms similar to slave cylinder leaks. To be sure of the leak source, inspect the inside of both the master and slave cylinders.

Other Symptoms

The slave cylinder will often squeak when the clutch is depressed due to rust build-up or other problems. Also, if the slave cylinder is faulty, you may experience problems shifting gears. The vehicle will often slip into a gear even when the clutch is pressed, or it may not shift at all.

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