The clutch system of a vehicle is a crucial component that enables smooth engagement and disengagement of power between the engine and the transmission. When there is a problem with the clutch slipping, it can significantly affect the performance and drivability of the vehicle. In the case of a Sinotruk truck-mounted crane with a pull-type control structure clutch, understanding the causes and solutions for clutch slipping is essential for ensuring the proper operation of the vehicle.
What’s the problem with serious clutch slipping of a truck-mounted crane of Sinotruk? After understanding that it is a Sinotruk truck-mounted crane and analyzing it for the user, it is found that his vehicle has a relatively common cause. After the separation bearing is abnormally damaged, the bearing steel balls and others fall between the cover and the diaphragm spring, resulting in slipping and poor separation. This is just one of the possible causes of clutch slipping, and there are several other factors that can contribute to this problem.
Vehicle clutch
In fact, for the fault of clutch slipping, we can generally divide the causes into three categories.
I. Reasons for cover assembly
Insufficient working pressing force of cover assembly
Before reaching the specified mileage in normal use, the attenuation of the pressing force of the cover assembly may exceed the tolerance. This can occur due to various reasons. For example, improper operations such as overloading the vehicle, getting stuck in mud and starting continuously for many times can cause overheating, burning or deformation of the pressure plate. When the pressure plate is overheated or deformed, it may not be able to apply sufficient pressure on the friction disc, resulting in clutch slipping.
Imagine a situation where a truck-mounted crane is overloaded with a heavy load and is trying to start on a muddy road. The excessive strain on the clutch can cause the pressure plate to heat up rapidly. As the temperature rises, the material of the pressure plate may start to lose its strength and shape, reducing its ability to press the friction disc firmly. This can lead to slippage between the friction disc and the flywheel and pressure plate, resulting in a loss of power transfer from the engine to the transmission.
Reasons for cover assembly
The working surface of the pressure plate is contaminated with oil.
(1) Before installation, the oil on the working surface of the pressure plate is not carefully cleaned. During the assembly process of the clutch, if there is any residual oil on the pressure plate, it can cause the friction coefficient between the pressure plate and the friction disc to decrease. This reduction in friction can lead to clutch slipping. For example, if a mechanic fails to thoroughly clean the pressure plate before installing it, any oil or grease left on the surface can interfere with the proper engagement of the clutch.
(2) Oil leakage from the rear oil seal of the engine crankshaft or the first shaft of the transmission. Oil leaks from these areas can find their way onto the clutch components, specifically the pressure plate and friction disc. The presence of oil can cause the friction material on the friction disc to lose its grip, resulting in clutch slipping. For instance, if the rear oil seal of the engine is damaged and starts leaking oil, it can seep onto the clutch and affect its performance.
(3) Excessive grease is applied to the spline of the first shaft or the bearing sleeve. When too much grease is applied to these areas, it can migrate and contaminate the clutch components. The grease can reduce the friction between the pressure plate and the friction disc, leading to slippage. Suppose a mechanic over-applies grease during maintenance, thinking it will help lubricate the parts. However, this excess grease can end up causing clutch problems instead.
Foreign objects are stuck between the cover and the diaphragm spring.
(1) After the separation bearing is abnormally damaged, the bearing steel balls and others fall between the cover and the diaphragm spring, causing slipping, shaking or poor separation. When the separation bearing fails, its components can break apart and get lodged between the cover and the diaphragm spring. This can interfere with the proper movement of the clutch components and cause slippage. For example, if the separation bearing wears out and its steel balls fall into the wrong place, it can disrupt the clutch’s operation and lead to problems with power transfer.
(2) Foreign objects in the cover are not cleaned before installation, so that they enter between the cover and the diaphragm spring, causing slipping, shaking or poor separation. During the installation of the clutch, if there are any foreign objects left in the cover, they can cause issues when the clutch is in operation. These objects can interfere with the movement of the diaphragm spring and affect the pressure applied to the friction disc. For instance, if a small piece of debris is left in the cover and gets between the cover and the diaphragm spring, it can cause the clutch to slip or not engage properly.
(3) Improper operation causes the clutch to burn out, so that the friction plate of the driven disc assembly falls off and enters between the cover and the diaphragm spring. Harsh or improper driving techniques, such as riding the clutch or constantly slipping the clutch, can cause the clutch to overheat and burn. In some cases, the friction plate of the driven disc assembly may fall apart and get stuck between the cover and the diaphragm spring. This can lead to serious clutch problems and require extensive repairs. For example, if a driver frequently engages the clutch partially or holds it down for long periods, it can cause excessive heat and damage to the clutch, potentially resulting in parts falling off and causing interference.
(4) The dust cover on the flywheel housing is not installed, resulting in foreign objects entering the cover and being stuck between the cover and the diaphragm spring. The dust cover plays an important role in protecting the clutch from external contaminants. Without it, dirt, dust, and other foreign objects can enter the clutch area and cause problems. For instance, if the dust cover is missing, small particles can get into the clutch and interfere with its operation.
Foreign objects stuck between the cover and the diaphragm spring
II. Reasons for driven disc assembly
The friction plate is contaminated with oil. Similar to the contamination of the pressure plate, if the friction plate of the driven disc assembly gets contaminated with oil, it can lose its grip and cause clutch slipping. This can happen due to oil leaks from the engine or transmission, or from improper handling during maintenance. For example, if oil drips onto the friction plate while the engine is being serviced, it can affect the clutch’s performance.
The friction plate is worn to the rivets and not replaced in time. As the friction plate wears down over time, it eventually reaches a point where the rivets holding the friction material start to show. At this stage, the friction plate is no longer able to provide sufficient grip and needs to be replaced. Continued use of a worn friction plate can lead to clutch slipping and damage to other clutch components. For instance, if a driver ignores the signs of a worn friction plate and continues to drive, it can cause the clutch to slip and eventually fail completely.
The friction plate is burned or cracked. Excessive heat or improper use can cause the friction plate to burn or crack. This can happen if the clutch is overheated due to prolonged slipping or if there is a problem with the cooling system. A burned or cracked friction plate will not be able to engage properly with the pressure plate and flywheel, resulting in clutch slipping. For example, if a driver continuously slips the clutch while driving up a steep hill, it can cause the friction plate to overheat and burn, leading to clutch problems.
Reasons for driven disc assembly
III. Reasons for the matching of cover assembly and driven disc assembly
Mismatch caused by using the driven disc assembly of other manufacturers. Using a driven disc assembly from a different manufacturer may not be compatible with the cover assembly of the clutch. This can lead to improper engagement and slippage. Different manufacturers may have different specifications and designs for their clutch components, and using mismatched parts can cause problems. For example, if a mechanic installs a driven disc assembly from a different brand without checking for compatibility, it can result in clutch slipping and poor performance.
Mismatch caused by using an inappropriate specification (including parameters) of cover assembly or driven disc assembly. Choosing the wrong specification or parameters for the cover assembly or driven disc assembly can also cause clutch slipping. This can happen if the wrong size, thickness, or material is used. For instance, if a driver replaces a worn clutch with a different specification than the original, it may not fit properly and cause slippage.
The control system is not completely reset, resulting in the clutch being in a semi-disengaged state and causing slipping. The clutch control system, including the master cylinder, slave cylinder, and linkages, needs to be properly adjusted and reset for the clutch to function correctly. If the control system is not adjusted properly, it can leave the clutch in a partially disengaged state, causing slippage. For example, if the slave cylinder push rod is not adjusted correctly, it can cause the clutch to not fully engage, resulting in slippage.
First, check whether the master cylinder, slave cylinder and pipelines are unobstructed. If they are not unobstructed, adjust them first. This step is important because any blockages or restrictions in the hydraulic system can affect the operation of the clutch. If there are problems with the master cylinder, slave cylinder, or pipelines, it can lead to improper clutch engagement and slipping. For example, if there is air in the hydraulic lines, it can cause a soft clutch pedal and poor clutch performance.
If the fault still cannot be eliminated, then disassemble and inspect the clutch. Here it should be noted that the gap between the push rod of the transmission cylinder and the piston should be checked and adjusted: During adjustment, gently push the pedal by hand to feel that the push rod of the transmission cylinder is against the piston of the transmission cylinder. Adjust the height of the limit bolt so that the gap between the limit bolt and the clutch pedal is about 0.5mm. Then tighten the nut at the limit bracket to ensure that there is a gap of 0.5mm – 1mm between the push rod and the piston. This gap should not exceed 1mm, otherwise the effective stroke of the transmission cylinder will be reduced. Proper adjustment of this gap is crucial for ensuring the correct operation of the clutch. If the gap is too large or too small, it can cause problems with clutch engagement and slipping.
In conclusion, clutch slipping in a Sinotruk truck-mounted crane can be caused by a variety of factors. By understanding these causes and taking the appropriate steps to diagnose and repair the problem, vehicle owners and mechanics can ensure the proper operation of the clutch and maintain the performance and reliability of the vehicle. Regular maintenance and proper driving habits can also help prevent clutch problems from occurring in the first place.
