Burning phenomenon of clutch release bearing:
Like an agricultural vehicle, when the clutch pedal is pressed, the engine is difficult to start. Using a hand crank to turn the crankshaft feels very heavy. Release the clutch pedal and shift to neutral to start the engine smoothly. When the engine is idling, simply press the clutch pedal and the engine will immediately shut down.
Park and turn off the engine for inspection. Press the clutch pedal and turn the driven plate. The driven plate can rotate freely and other components are not damaged. Pulling the clutch release bearing, it was found that the release bearing could not be moved. After dismantling and inspection, it was found that the release bearing was eroded due to poor lubrication, and its inner and outer rings, as well as the retainer and other parts, were severely eroded and locked. During operation, the bearing not only cannot rotate, but also generates significant friction and abnormal noise with the clutch release lever, causing difficulty in starting the engine.
The common causes of damage to the separation bearing are:
1. Although lubricating grease has been added to the separation bearing when it leaves the factory, after long-term use, especially when exposed to high temperatures, the grease melts and is gradually stripped away during bearing operation. The bearing experiences dry friction and generates heat, leading to erosion, jamming, and loss of separation function.
2. Some drivers are accustomed to using a half foot clutch, which puts the clutch in a semi engaged and semi disengaged state, causing dry friction in the clutch and heat transfer to the release bearing, resulting in the loss of lubricating grease in the bearing. When the temperature reaches a certain value, the bearing burns and is damaged.
3. During vehicle maintenance, if a small oil pan is missed or lost, mud and dirt may enter the separation bearing, causing bearing wear.
4. The clutch pedal has too little or no free travel, causing it to be in a state of frequent engagement, resulting in fatigue damage or even erosion; The pedal travel is too large, causing incomplete clutch disengagement and difficulty in shifting. The clutch is in a semi engaged and semi disengaged state, generating dry friction and heat transfer to the release bearing, causing the lubricating grease to flow out and the bearing to burn away.
5. After the separation shaft is subjected to dust erosion, the lubricating grease deteriorates, exacerbating its damage.
6. The separation bearing and separation sleeve have poor fit, especially with excessive clearance, looseness, and not being in the same plane. During operation, the separation shaft bears impact loads, causing wear and erosion of the track.
The separation bearing should rotate flexibly without abnormal noise (inspection method, axial clearance), and the wear of the inner race should not exceed 0.3mm, otherwise a new part should be replaced. The clearance between the pedal shaft and the separation fork and the bushing is too large. Generally, the bushing should be replaced and fitted by grinding. When cutting two bushings on the bracket, a long blade cutter or a guiding blade must be used to ensure their coaxiality.
When the engine is idling and the clutch pedal is pressed, if you hear a "sand, sand" or "clang, some" sound, lift the clutch pedal and the sound disappears. If you press the clutch pedal again slightly (to make the release bearing contact the release lever), the friction sound will appear again, indicating that the clutch release bearing is short of oil or worn.
When disassembling and inspecting the separation bearing, first unscrew the fixing screws and bolts of the separation lever from the transmission housing, remove the separation lever, take off the separation bearing assembly and fixing spring, and then use a puller to pull the separation bearing off the separation bearing seat. Check the separation bearing. If there is a lack of oil, it should be replenished. If it is worn, it should be replaced. When assembling the separation bearing, apply an appropriate amount of lithium molybdenum disulfide based grease to the area indicated by the arrow on the separation bearing seat. The amount should not be too much to avoid contaminating the driven disc.
Separable bearings generally use axial thrust ball bearings, which are press fitted onto the separable sleeve. Lubricating grease or engine oil is regularly added through a specially designed oil nozzle installed on the flywheel housing to lubricate the working surface of the separable sleeve and the separable bearing. Some separation bearings use well sealed pre lubricated bearings, which are not allowed to be cleaned with gasoline or lubricated during disassembly and assembly. They only need to be wiped clean.