Slave Cylinder Replacement

Rehabbing hydraulic-clutch systems

Manual transmissions' popularity is dwindling. For daily commuting in stop-and-go traffic, automatics are a lot easier on the legs and brain—not to mention that less driving skill is required to operate them.

But stick shifts have always had a couple of advantages over their newer-fangled comrades. For one, manuals let more of the engine's power pass through to the axles, so they help improve fuel economy. Also, true sports-car aficionados occasionally like to redline their engines and don't want an auto-trans deciding when they should shift. Further, people who tow with their SUVs or do slow-speed off-roading often prefer the "lower" (slower) gearing offered by a stick compared to an automatic.

Most modern manual transmissions use hydraulics to engage and disengage the clutch. Hydraulic clutches are similar to brake systems. Just as depressing the brake pedal dispatches fluid that moves pistons, which in turn spread shoes or tighten pads to stop the vehicle, stepping on the clutch pedal in a hydraulic system sends fluid to a slave cylinder, where a piston and rod move the clutch-release lever.

Troubleshoot

Hydraulic clutches are similar to brake systems. Philosophically, hydraulic-clutch and brake problems are similar. When the pedal goes straight to the floor with little resistance, some is afoot in the system. First, check the fluid level in the clutch's master cylinder. (Most take DOT 3 brake fluid.) Then look for leaks at all the clutch-line connections. A faulty master cylinder will often cascade fluid down the firewall, sometimes onto the floorboard.

If the problem persists, bleed the slave cylinder as you would a brake cylinder or caliper. Still no clutch engagement/disengagement? The clutch itself usually emits sounds and smells as it dies, so abrupt failure normally indicates a problem upstream from it.

The photos here provide an overview of how to replace a clutch slave cylinder. The job can be messy, but it's pretty straightforward. Best of all, taking care of the problem will get your vehicle moving straight-forward again—and side-to-side.