The wheel loader is often applied in the harsh environment involving construction site, port, wharf, station, freight yard, etc. for loading or short-distance transporting loose earth, sandy clay, sandstone, coal, trash and so on. For the machine always works under complex conditions and bad environment, plus the factors such as design, manufacturing and use, the reliability of the wheel loader is reduced largely. According to the practical experience, we make a summary about the fault reasons of the wheel loader.

1. Design Defect
The structure of the wheel loader is complex. The working status of each assembly and part has large difference. As a result of the designer lacking of fully consideration and understanding about the working conditions of the wheel loader, some of the parts cannot completely adapt to the needs of various operating conditions in operation. Then, in the practical service process, the design defect is exposed to cause the fault.

2. Assembly Manufacturing Defect
The part manufacturing process doesn't follow the technological requirement strictly or the technological process is not reasonable can cause that the designed geometrical shape or mechanical property of the parts could not be guaranteed. Thus, the parts may be damaged in the early phase.

During the assembly process, for the reason of improper adjustment or failing to adjust, the fit clearance of the parts can not meet the necessary technical requirements, thus destroying the mutual positions of the parts assembly, and then causing early damage of the parts and affecting the technical condition of the wheel loader. In addition, for lacking of necessary detection means before assembly, the improper selection and inspection of the parts may result in damage to the wheel loader.

3. Influence from External Conditions during Operation
The external conditions influencing the wheel loader mainly contain weather condition (high temperature, tropical zone, plateau, etc.), working site and working object. The too high temperature could easily lead to bad cooling effect of diesel engine, thus causing overheating of machine and decreased lubricating oil viscosity bringing about poor lubricating effect. If the temperature is too low, the thermal efficiency of the diesel engine is decreased with the consequent impaired economical efficiency and increased lubricating oil viscosity. Then, the lubricating condition becomes poor, accelerating the wear of the engine parts. The low temperature can also make the startup of the diesel engine become difficult.

The working site and working object have a large influence on the serving lifetime of the wheel loader. Working in the rough and rugged site, the machine would bump and vibrate violently. The structural parts of the wheel loader would damage easily. The high-density working object would cause damage to the working device. Something harmful such as the gravel in the field may scratch the tire to shorten its lifetime. The dusty working site can also create fast early wear of diesel engine.

4. Improper Use of Oil
During the operation, for keeping the normal work of the wheel loader, the user should reasonably select the applicable fuel, lubricating oil (grease), hydraulic transmission oil, hydraulic oil, gear oil, brake fluid, etc. Otherwise, the improper oil could aggravate the wear of the assembly and parts of the wheel loader. Then, the use performance is reduced and the technical condition deteriorates.

The quality of the diesel oil has a great impact on the wear of the diesel engine's parts. Bad diesel oil has poor evaporation, leading to extended after combustion period. Then, the diesel engine would work with bad state and the wear of the parts is accelerated.

The lubricating oil quality directly affects the lubricating effect. The viscosity is an important index of lubricating oil. Too large viscosity means poor flowability. Too small viscosity would result in failed forming of lubricating oil film on the matched friction surface with the result of aggravating the wear of the engine parts. The hydraulic transmission system, working hydraulic system and other systems also have high requirements to the oil. Inappropriate selection may cause adverse effect to the transmission system and hydraulic system.

5. Improper Operation
Because the operator is not familiar with the operating procedures or not well trained to operate the machine coordinately, the inattention and improper operation of the operator can damage the wheel loader or generate the accident during the driving or working process.

The overload operation of the wheel loader is also a noticeable factor initiating the parts damage even the accident. During the working process, the frequent overloading or long-time high-intensity running would give rise to fast temperature rise and high temperature of the wheel loader, thus damaging the machine parts too early.

6. Inappropriate Maintenance
The regular maintenance for the wheel loader is very important on accounting of the bad working conditions. Many severe faults originate from the inappropriate maintenance. The cases such as maintenance failing to follow the provisions of technical requirements, improper assembly and adjustment during repair or poor quality of accessories would cause frequent occurrence of the fault.