Start the engine and gently step on the clutch pedal. When the clutch bearing is in contact with the separation lever, the sound of "sand sand" is heard and the pedal is lifted and the noise is disappearing. It can be concluded that the clutch separation bearing is lacking in oil or bad lubrication. If the clutch pedal is stepped on, the "clutching" metal dry friction sound is sent out, and the clutch bottom is removed. If there are ablative and discoloring marks at the contact of the clutch bearing and the separation lever, the clutch bearing is not turned or damaged. If the engine is started, the sound of the intermittent bearing is heard, the clutch pedal is hooked and the noise disappears, which is mainly caused by the falling off of the pedal spring or the weakness of the pedal. Sometimes, when the bearing spring is too soft, stretched or broken off, the bearing will always hear noise. The bearings are short of oil and should be added. If the bearing is stuck, damaged or worn out, new parts should be replaced.