What Causes a Clutch to Fail to Disengage?
2 Answers
There are several reasons why a car clutch may not disengage completely: 1. Excessive free travel of the clutch pedal reduces the distance the release bearing pushes the release lever forward, consequently shortening the travel of the pressure plate backward, preventing the clutch from fully disengaging. 2. In a dual-plate clutch, if the adjustment screw is too close to the intermediate drive plate, it limits the rearward movement of the intermediate drive plate, causing incomplete separation from the front friction disc. Conversely, if the adjustment screw is too far from the intermediate drive plate, excessive rearward movement may cause the intermediate drive plate to collide with the rear friction disc, also resulting in incomplete disengagement. 3. Significant differences in length or stiffness of the front pressure plate springs, damaged springs, uneven spring hole depths, warping of the inner or outer clutch disc assemblies, or loose rivets can cause the radial and axial runout of the clutch assembly to exceed specifications, leading to intermittent contact. 4. Improper adjustment of the gap between the hydraulic cylinder piston and the push rod in a hydraulically operated clutch.
The clutch can't escape this issue. I've encountered it a few times in over twenty years of driving, and it's quite a headache. The most common problem is rust on the clutch disc, especially after rainy days or when the car hasn't been driven for a long time. Rainwater seeps in and causes it to stick, making the clutch pedal feel stiff. Another possibility is an issue with the hydraulic system, such as a leaking master cylinder or insufficient brake fluid, which prevents proper pressure delivery and incomplete disengagement. Driving habits also play a role—some people tend to drive with the clutch partially engaged, which can cause excessive wear and overheating, leading to the clutch sticking together. If this happens, don't force-start the car. Instead, try pulling the handbrake and gently pressing the clutch to see if you can shake it loose in the opposite direction. If that doesn't work, call a tow truck. Otherwise, the car might lurch forward when starting, which is very dangerous—my neighbor once had a minor accident because of this. To prevent this, avoid parking in damp places for extended periods and occasionally start the car to let the clutch dry out.
