1. The sealing of the joint surface is not tight due to the damage or reverse installation of the sealing element:
2. The size fit clearance of relative moving parts is too large, or the clearance is too large due to long-term movement wear;
3. The box casting has air hole, sand hole and other defects;
4. Operating temperature is too high or lubricating oil viscosity is too low;
5. The lubricating oil pipe is deformed or cracked, resulting in oil leakage.
