As an important part of the transmission system, the clutch has the same lifespan as the car under normal use. There is a technical standard "Automotive Dry Friction Clutch Assembly Technical Conditions QCT25-2004". The clutch cover assembly needs to go through 1 million times. After the separation durability test, the main performance parameters are still 70% to 90% of the original. It can be seen that the clutch is very durable. According to the experimental statistics, the domestic urban roads step on the clutch almost 9 times per kilometer, and the suburban areas step on the clutch 3 times per kilometer. If the two road conditions are 50% each, it is calculated as an average of 6 clutches per kilometer. After more than 160,000 kilometers, the performance of the main parts of the clutch is still very good.
Service life of clutch friction parts Don't worry too much about the normal service life of friction parts. The main parts are not easy to be damaged or there are vulnerable and consumable parts. It is often said that the clutch is a three-piece set, which is the clutch plate, the pressure plate and the release bearing. The clutch plate is the main friction part of the clutch. It is generally made of asbestos-based friction materials. Now there are also semi-metallic, composite fiber, and ceramic fiber friction materials. This is a relatively expensive car. The operating temperature of the clutch is about 200°C, and the normal service life is relatively long.
The clutch pressure plate and the clutch plate should be replaced together. The life of the clutch pressure plate is theoretically more than twice that of the clutch plate, so the clutch plate is installed on the pressure plate. Now many manufacturers install the clutch plate and the pressure plate directly. Sets are sold together. The two must be replaced together with the same service life. You said that the pressure plate can still be used for a while, and the clutch plate may be replaced. The release bearing has a service life of more than 100,000 kilometers. Another thing is the release bearing, which is a part of the clutch combination and release actuator, and it also has standards. "Mechanical Industry Standard JB/T 5312-2001 Automobile Clutch Release Bearing and Its Unit" stipulates that the regulations were so early, and the cars were not very good at that time. The bench simulation life of the release bearing should not be less than 1 million times, and other models should not be less than 500,000 times. Some reasons that lead to the short service life of the clutch. If the three-piece clutch is not operated properly, the service life will be shortened quite a lot. There are also times when it hangs up after more than 10,000 kilometers.
Generally speaking, it is generally only when the clutch fails that it needs to be replaced. Generally speaking, there is no problem when using 100,000 kilometers.
Symptoms of a bad clutch plate:
1. The clutch plate slips during rapid acceleration
The performance is that when the accelerator is stepped on deeply, the engine speed can rise rapidly, but the vehicle speed does not increase much. This is where the clutch plates are slipping, causing the engine to idle and not all power being delivered to the gearbox. This is the easiest to feel, whether you drive your own car or someone else's car, you can feel it. The easiest way is to put in 1st gear, pull up the handbrake (or step on the brake) and start, if the engine is not turned off, then replace it.
2. Can’t run at high speed. When the speed of 5th gear is 100 per hour, you suddenly step on the accelerator to the bottom. When the speed increases obviously but the speed does not accelerate much, it means that your clutch is slipping and you need to change the clutch plate.
3. The clutch becomes higher
It means that when the car is lifted a little, the clutch is engaged and the car can move forward. Now it has to be lifted very high, the clutch can be engaged, and the car can only move forward. This is also a phenomenon that the clutch plate is thin. However, many people often do not feel it, because their car is driven every day, and the clutch is gradually raised up little by little, so it is not easy to notice. As it rises, they can also adapt to this height, so they will not I feel abnormal.
4. The sound of metal friction can be heard every time the clutch is lifted, which may be due to serious wear of the clutch plate. The car is tired of climbing hills; after driving for a while, you can smell the smell of being burned.
5. The clutch surface is uneven
Also needs to be replaced, be it thick or thin. The phenomenon is that when starting, the vehicle shakes violently, and when half-clutching, the shaking is severe, which means that the clutch surface is uneven. This situation is mostly due to the quality of the clutch plate. Start in first gear, feel uneven when clutching, the car has a forward and backward jolting feeling, press the plate, step on it, and feel jerky when lifting the clutch, the clutch plate needs to be replaced.
Common failure symptoms, causes and diagnosis methods
1. Clutch slipping
Symptoms:
① Insufficient power when starting or going uphill with heavy load;
②The engine accelerates weakly while driving. In case of severe slippage, the friction plate of the clutch will emit smoke, have a burnt smell, and even burn the friction plate.
cause of issue:
① The free travel of the clutch pedal is too small or absent;
②The surface properties of the friction plate change, such as oil stains, ablation, hardening, cracking, rivet exposure, etc.;
③ The elastic force of the clutch pressing spring is weakened or broken, so that the insufficient pressing force causes slipping;
④The wear of the pressure plate is too thin, so that the compression spring stretches too much;
⑤Warping and unevenness of the main and driven discs lead to poor contact.
Fault diagnosis method:
①Start the vehicle, tighten the parking brake, put in a low gear, and start the vehicle normally. If the body does not move but the engine does not turn off, it means that the clutch is slipping;
②Do not start the vehicle, put in a low gear, tighten the parking bake, and shake the engine with the handle without stepping on the clutch pedal. If it can shake, it means that the clutch is slipping.
2. The clutch is not completely disengaged
Symptoms:
①Start the vehicle, put in low gear, release the parking brake, and the vehicle will drive or turn off when the clutch is not released
②When the engine is idling, the clutch pedal is depressed, and it is difficult to engage the gear, accompanied by the sound of the transmission gear hitting.
cause of issue:
①The free travel of the pedal is too large, resulting in insufficient travel of the pressure plate when separating;
② The height of the separation lever is inconsistent;
③ The main and driven discs are warped and uneven;
④The spring force of the pressure plate is inconsistent or broken.
Fault diagnosis method: When the car is not started, two people cooperate to judge. One person puts the transmission into the first gear, depresses the clutch pedal, and the other person shakes the engine with the handle. If it does not shake or the vehicle has a tendency to move forward, it proves that the clutch is not completely disengaged.
3. Clutch shaking
Fault phenomenon: When the car is in gear and starts, the clutch impacts intermittently, and the whole body trembles.
Cause of failure:
①The height of the separation lever is inconsistent;
②The elastic force of the compression spring is unevenly distributed or broken individually, and the rivet of the friction plate is loose;
③Warping and deformation of the main and driven discs;
④The spline of the driven disc hub is severely worn.
Fault diagnosis method: Let the engine run at a low speed, put on a low gear and start slowly. If the car continuously impacts at this time, it means that the clutch is shaking.
4. The clutch sounds
Fault phenomenon: There is abnormal noise when the clutch is disengaged and engaged.
Cause of failure:
①Separation bearing beeps due to lack of oil;
②The release bearing is damaged and sounds;
③The matching gap between the pressure plate and the transmission pin of the double-disc clutch is too large;
④The gap between the key teeth of the driven disc hub and the key teeth of the first shaft is too large;
⑤ The rivets of the driven disc hub are loose.
Fault diagnosis method: Put the transmission in the neutral position, let the engine run at idle speed, step on or loosen the clutch pedal (disengage or engage), the sound is more obvious when the car is not moving.
5. The clutch pedal feels weak, and the clutch fails to work
Symptoms: When stepping on the clutch pedal, it feels soft, like stepping on a balloon, and the clutch does not disengage.
cause of issue:
① The oil storage tank of the hydraulically operated clutch is short of oil;
②The oil pipe or joint from the master cylinder to the working cylinder has oil leakage, or the air release screw on the working cylinder is loose and leaks oil.
Fault diagnosis method: Open the engine compartment cover of the car to check the oil volume of the clutch oil storage tank. If there is no oil, follow the oil pipe to find out whether there is leakage, and find out the reason for the decrease in oil volume. If there is no obvious leakage, check whether the gap between the release bearing and the release lever is too large, resulting in a large displacement of the working cylinder piston and rubber bowl, and more oil required. If there is no shortage of oil, the main reason is that the piston and cylinder of the hydraulically operated main cylinder are worn, making the matching gap too large, and the piston is out of shape when it moves; the rubber bowl of the main cylinder is damaged and deformed, which reduces the sealing performance and causes compressed oil. It flows back to the back of the rubber bowl and the piston, causing the actual oil supply to be insufficient.
6. The clutch pedal is heavy
Fault phenomenon: For the clutch equipped with a pneumatic booster or oil-pneumatic booster control mechanism, if the clutch pedal feels obviously heavy when you step on it, if you have to use a lot of force, it indicates that the booster system is not working well.
cause of issue:
① Insufficient air pressure or air leakage in the pipeline system, resulting in insufficient air pressure and poor power assisting effect;
②Piston sealing ring of air pressure cylinder is worn, or the exhaust valve is not tightly sealed, which reduces the boosting effect;
③The follow-up control valve fails, making the booster work poorly.
Fault diagnosis method: Check the wear condition of the cylinder body of the oil-gas booster and the working surface of the follow-up control valve body to see if there is any corrosion; check the movement of the piston in the cylinder, it should be flexible and free of stagnation, and the piston should be replaced if it is seriously worn New parts, if the rubber sealing ring is worn, it should be replaced; check whether the spring is rusted or damaged; check whether the contact surface of the valve group parts is damaged or other defects. In addition, too thick driven disc will also increase the compression force of the spring.
How to reduce the loss of clutch plates in daily driving:
1. Do not step on the clutch when not shifting gears
2. The semi-linkage time should not be too long, and shift gears reasonably according to the road conditions
3. When parking, take neutral gear and release the clutch pedal
4. Use first gear when starting to reduce clutch overload