Many operators have started performing their own machinery maintenance, which is a positive trend. It shows that technicians are recognizing the value of technical work—because skilled maintenance is highly valuable.

However, mastering maintenance is not something that can be learned in a few days. It requires both effort and a certain level of innate talent. Some people learn quickly, while others may struggle throughout their entire career.

Maintenance involves techniques, skills, and component quality, but the details are crucial. Even if you’re just replacing parts, how you do it makes a huge difference. For example:

• Some people understand the importance of disassembling and assembling machinery in a clean environment, while others work in mud and still dare to take apart hydraulic pumps.

• I remember a case in a state-owned enterprise: a Nissan RD6 diesel engine, assembled in a very dusty environment. After a 3-hour test run, it scored the cylinder, requiring a complete reassembly.

Lesson: Small details can lead to major problems—this knowledge cannot be fully learned online.

Hydraulic Oil and Component Quality

Many forum members report slow or sticky machine actions. Often, the root cause is hydraulic oil quality or filters.

1. Select a reliable brand

   • Even “budget” domestic brands (e.g., Great Wall) are acceptable, but purchase from official company outlets or state-owned gas stations to avoid counterfeit products.

2. Choose the correct viscosity

   • Don’t follow others blindly. For northern cold regions using plunger pumps:

     • Use low-temperature anti-wear hydraulic oil in winter.

     • In summer, do not exceed ISO VG 32.

   • For gear pump machines, anti-wear ISO VG 46 is acceptable in summer.

   • Explanation: The plunger shoe clearance in plunger pumps is a weak point. Slow machine actions are often due to excessive axial clearance, not pump wear.

   • Cold start whining may indicate filter issues or vacuum problems, but most often it is oil viscosity related.

• OEM recommendations: CAT and Komatsu typically specify ISO VG 10 / 10W. I have experienced machines running 30,000 hours without repairing pumps or motors when using correct OEM oils, even in harsh limestone quarry environments.

3. Use parts from the same manufacturer

   • Mixing brands in precision assemblies (pumps, motors) can cause premature wear and failure, even during initial test runs.

4. Use a torque wrench correctly

   • Don’t rely on brute force. Follow specified torque values and sequences.

   • Torque wrenches must be calibrated regularly. Advanced assembly may also involve torque + angle control.

5. Maintain strict cleanliness during assembly

   • Avoid using tissue paper or rags that may shed fibers into precision components.

   • Compressed air or aerosol cleaners can help, but always lubricate parts with clean hydraulic oil before assembly.

6. Offline testing before installation

   • Test precision components (pumps, motors) outside the machine to reduce rework.

   • Custom fixtures can help ensure correct operation before assembly.

7. Replacing final drive taper seals or hydraulic motor seals

   • Don’t just replace the seal—identify the root cause: wear, oil quality, overheating, or bearing damage.

   • Misadjusted bearings, such as deep groove thrust ball bearings, can shorten service life if tolerances are incorrect.

8. Small excavator cycloidal final drives

   • Complex structure and bearing adjustment make repair challenging. Many operators end up replacing the entire assembly.

Summary

• Proper hydraulic oil selection, precision component handling, and assembly cleanliness are essential for reliable machinery operation.

• Following these principles prevents premature wear, reduces downtime, and maintains machine performance.

• Future discussions will cover reducer components, bearing selection, and usage tips to help technicians build fundamental knowledge.