If a hydraulic clutch pedal has no pressure, what may be leaking?

When a hydraulic clutch pedal has no pressure, the most likely source of the issue is the slave cylinder. The hydraulic system for a clutch relies on fluid to create pressure, which pushes the clutch release mechanism. If there is a leak in the slave cylinder, hydraulic fluid can escape, leading to a loss of pressure in the system. This makes it impossible for the driver to engage or disengage the clutch properly. Identifying and addressing leaks in the slave cylinder is crucial to restoring functionality to the clutch mechanism.

In contrast, while axle seals, rear seals, and wheel cylinders may also leak hydraulic fluid, they are not components directly involved in the clutch system. Their failures would generally affect either drivetrain performance or braking rather than directly impacting clutch pedal pressure.