A clutch release bearing is located between the clutch fork and the pressure plate and is essential in the clutch operation. When a driver presses on the clutch this creates pressure, which is turned into hydraulic pressure in the clutch master cylinder and is transferred to the rod. This pressure is then exerted on to the clutch release bearing which lastly pushes on the pressure plate and disconnects the engine when you bring it to a stop. This enables you to change gears.
One major cause of damage to a clutch release bearing is waiting in traffic with the clutch disengaged but vehicle in gear. The excessive load causes stress to the clutch release bearing. Issues with the clutch release bearing are serious and should be rectified immediately. The most noticeable symptom is a grinding or whirring noise when applying the clutch, which goes away when you release the clutch pedal. This indicates that the clutch release bearing is wearing out and may seize. If the bearing fails it will cause wear to the pressure plate and the attached clutch disk. A complete clutch replacement may be required.