What causes the sudden stiffness when pressing the clutch in a Hyundai Elantra?

[DelJoel]

Possible reasons for the sudden stiffness when pressing the clutch in a Hyundai Elantra include a malfunctioning clutch master cylinder. For instance, the return spring of the master cylinder may be broken or stuck, the rubber cup may be swollen or flipped and stuck at the compensation hole, or the one-way valve at the end of the master cylinder may be stuck and not returning to position. Below are specific details about the clutch master cylinder: 1. Overview: The clutch master cylinder is the part connected to the clutch pedal and linked to the clutch booster via a hydraulic line. Its function is to collect pedal travel information and, through the booster, enable the clutch to disengage. 2. Precautions: If the clutch master cylinder is damaged, avoid forcing the gear shift as it will accelerate wear. Typically, the solution for a damaged clutch master cylinder is direct replacement.