A clutch release bearing, also known as a clutch throwout bearing, is an important part of the automotive transmission system, located between the clutch and the transmission. Its main function is to push the release lever (or release fork) through a series of mechanical linkages when the driver operates the clutch pedal, thereby separating the pressure plate from the slave plate and interrupting the power transmission from the engine to the transmission, allowing the driver to shift gears without interrupting the smooth operation of the vehicle. 

The release bearing is designed to withstand axial loads, shock loads, and radial centrifugal forces generated during high-speed rotation. Because it operates in an environment with high friction, high temperatures and difficult direct lubrication, high requirements are placed on the bearing's high temperature and wear resistance. To ensure their proper functioning, separation bearings require good lubrication, which is usually achieved through specific greases or, in some designs, through forced lubrication systems. In daily use, damage to the release bearing is often associated with improper operation, inadequate lubrication, improper free travel or wear, and regular inspection and proper maintenance are essential to extend its service life.

 Clutch Release Bearing Failure Symptoms and Inspection and Maintenance Methods

 Clutch release bearing failure symptoms

1. Abnormal noise

   - When depressing the clutch pedal: a ‘rustling’ or ‘clattering’ sound may be heard, especially when slipping in neutral gear. This is due to lack of lubrication or wear of the release bearing.

   - When driving in gear: If you hear a sound like metal rubbing, this may be a sign of damage to the release bearing, but it does not affect normal driving.

2. Abnormal clutch operation

   - Incomplete separation: After depressing the clutch pedal, if you feel that the clutch does not separate cleanly, it is difficult to shift gears or there is a sense of stuttering, this may be a problem with the release bearing.

   - Heavy pedal feel: If the clutch pedal becomes harder to press than usual, it may be because the release bearing is stuck increasing the resistance of the pedal.

   - Unusual starting difficulty: In extreme cases, such as that shown in the example of the Dongfeng Agricultural Vehicle, where the engine is difficult to start, it may be due to a faulty clutch system caused by a damaged release bearing.

3. Immediate signs of wear and damage

   - Physical inspection: If during inspection the release bearing is found to be rotating inflexibly, with obvious play or seizing, this is an indication that the bearing has been damaged.

   - Lack of oil or severe wear: When the release bearing is out of oil or severely worn, a noticeable rubbing sound may be heard when the clutch pedal is depressed while the engine is idling.

4. Affecting the driving experience

   - Prolonged abnormal sound and poor operation: It will directly affect the driving comfort and safety.

5. Other potential problems

   - Clutch pedal vibration: When depressing or releasing the clutch pedal, an abnormal vibration of the pedal may be felt.

   - Clutch slippage: When accelerating, the engine speed increases but the vehicle speed does not, this may be caused by slippage due to incomplete engagement between the clutch disc and the flywheel.

   - Difficulty shifting gears: Resistance may be encountered when attempting to shift gears, especially when starting from a standstill.

   - Vehicle will not start: If the clutch release bearing is severely damaged, this may result in the vehicle not engaging the clutch properly when attempting to start.

   - Clutch system leaks: For hydraulic clutch systems, if the seals around the release bearing are damaged, hydraulic fluid leaks may occur.

   - Transmission Damage: prolonged periods of incomplete clutch disengagement may result in damage to internal transmission parts due to excessive wear and tear, as evidenced by increased transmission noise or abnormal function.

 Clutch Release Bearing Inspection Procedure

1. Symptom identification

   - Confirm whether there is any abnormal noise, difficulty in shifting gears, or abnormally heavy clutch pedal.

2. Engine idle speed check

   - Depress the clutch pedal and listen for a ‘rustling’ sound. If the sound disappears, the release bearing may be out of oil or damaged.

3. Physical check

   - Disconnect the power supply to ensure safety.

   - Remove the gearbox and clutch cover and check whether the release bearing can rotate freely and whether there is any stagnation or abnormal wear.

4. Gap measurement

   - Measure the axial clearance between the release bearing and the release lever to make sure it is within the normal range (usually less than 0.6mm).

5. Lubrication condition

   - Check the lubrication condition of the bearing, if the bearing is dry or the grease is exhausted, it needs to be replaced.

 Clutch Release Bearing Repair Procedure

1. Disassembly

   - Remove the clutch pressure plate, slave disc and then the release bearing. This usually requires lifting the transmission off the vehicle.

2. Replace the release bearing

   - If the release bearing is damaged, replace it with a new one. Be careful to select a model that matches the original.

3. Inspect related components

   - Check the breakaway lever, breakaway fork and return spring to make sure they are in good condition and not deformed or damaged.

4. Lubrication and assembly

   - Apply a suitable amount of molybdenum disulphide lithium grease to the release bearing housing, taking care not to contaminate the clutch disc with the grease.

   - When reassembling, make sure all parts are installed correctly and adjust the free travel of the clutch pedal.

5. Testing

   - After completing the assembly, start the vehicle and check whether the clutch operates smoothly and there is no abnormal sound.

 Precautions

1. Follow the instruction manual: Follow the vehicle manufacturer's instruction manual when servicing. 

2. Use specialised tools: Ensure safe and correct disassembly and assembly.

3. Professional Repair: If you are not familiar with this operation, it is recommended that it be carried out by a professional mechanic to avoid further damage or safety hazards.

With these detailed steps, you can effectively diagnose and repair clutch release bearing problems to ensure the normal operation of your vehicle and driving safety. I hope this information is helpful to you!