Let’s continue talking about the importance of machine inspection and maintenance.

In fact, the user manuals provided by manufacturers only meet the minimum operating requirements. If, during use, you are still reluctant to spend a little money on inspection and maintenance, it’s truly disappointing.

I want to emphasize: I have no business interests with fellow operators, I never promote spare parts or materials, and I always advocate focusing on inspection and preventive maintenance rather than just repairs. So, what I say is based on real experience.

Inspection and maintenance are absolutely necessary, not superfluous.

Every machine has an economic service life. After that period, maintenance costs will continue to rise until the machine is scrapped. Determining this service life depends on your own statistics and experience. Even within the same batch of machines, the economic life cycle may vary slightly, but generally not by much (unexpected failures excluded). That’s why pre-shift checks and scheduled maintenance are so important. Don’t rely solely on repairs—it’s like relying on the fire department. If you wait until they arrive, your house is already almost gone.

Case Examples

1. Shandong XZ area:
   An excavator 320BL worked in coastal mudflats. One travel reducer was leaking oil, but it wasn’t repaired in time. The machine kept running until the travel failed completely. By then, the reducer was completely ruined—beyond repair. The whole assembly had to be replaced—costing over 100,000 RMB.

2. Shandong XA:
   An excavator had a swing reducer leaking oil. Someone had the “bright idea” of filling it with grease instead. Indeed, it stopped leaking—but soon the reducer seized up and stopped turning. Not only was the reducer scrapped, but the swing motor spline shaft was also damaged.

3. Anhui, XC:
   On a rainy day, I walked past a CAT336D2 and noticed one side of the travel reducer was oddly dry, while the other side was wet from rain. I stopped the operator, touched the reducer, and it was burning hot. I told him to shut down immediately. Luckily, it was stopped just in time, otherwise the consequences would have been much worse.

4. South Shandong:
   A CAT320C (non-electronic control model) owner used cheap diesel filters costing 30 RMB instead of the proper ones costing over 100 RMB. He was proud of saving money. Within days, the injection pump failed.

5. A large state-owned enterprise:
   At a quarry dam project, a famous-brand diesel compressor consumed about a ton of diesel every two days, requiring frequent filter changes. To “save time,” workers removed the filter element entirely. Within three days, the fuel pump plunger wore out and failed. At that time, repairs had to be sent to Beijing—costly and time-consuming.

These failures were all caused by poor maintenance practices. With proper inspection and care, none of them would have happened.

Key Points

• Swing and travel reducers must have their oil replaced on schedule.

  • Not only to refresh old oil, but also to check for signs of failure.

  • Replacement is cheap insurance compared to the cost of replacing the entire reducer assembly.

• For excavators, the swing reducer is especially critical. Except for mini-excavators (which may use hydraulic oil as common lubrication), most models have independent lubricating oil, and larger machines may have two identical swing reducers.

  • Typically, a 20-ton machine requires only about 5–8 liters of oil, replaced every 1,000 hours.

  • Even using ordinary brands of oil is fine—just don’t skip it.

  • Always inspect the drained oil. If it contains excessive metal particles, the reducer must be serviced immediately.

• Machines never get better through repeated repairs. At best, they can be kept running.

• Many roadside repair shops only “fix what’s broken,” like replacing seals when reducers leak. But if root causes aren’t addressed, leaks will return quickly.

• For travel reducers, don’t use excavators like taxis—constantly running long distances in high-speed gear (“rabbit gear”).

  • During the Qinghai-Tibet railway project, some excavators ran more than 10 km daily in rabbit gear. As a result, travel reducer seals frequently failed.

  • Use trailers for long relocations. If driving is unavoidable, use low gear (“turtle gear”).

• Don’t fill leaking reducers with grease as a “fix.” This only destroys components faster, eventually requiring total replacement.

• For fuel filters, never reuse dirty diesel inside discarded filters. That’s contaminated fuel. No matter the filter brand, their rated efficiency only applies under proper conditions. A clogged filter means small impurities have already entered the fuel system.

• Both traditional fuel systems and modern common rail systems can be damaged by poor fuel quality. Example: over 20 years ago, an imported Mitsubishi 8V engine fuel system failed in just over a day because smuggled diesel had high water content. Pump plungers rusted and seized.

• Engine oil must also be changed on schedule. Someone once told me they had run engine oil for about 1,000 hours—it’s impossible for the machine to stay in good condition under such neglect.

• Loader transmission oil and filters must also be changed regularly. Otherwise, the transmission pump, clutch plates, and brake plates wear excessively, increasing repair costs.

• Hydraulic oil is the same. You can’t judge its quality just by appearance. The additives degrade over time and cannot be “restored.” Filtering old oil or adding magnetic filters is a false sense of security. Worn machines constantly generate metal debris—eventually, failure is inevitable.

• Pre-shift inspections are vital, especially for double-shift operations. Neglecting them can lead to catastrophic damage or even machine write-offs.

• Many operators complain online about poor machine quality when booms or arms crack. In reality, did they ever check for cracks beforehand? Inspections could at least reduce losses.

• One real example: a CAT M315D2 wheeled excavator was operating near piles of dry leaves. The operator ignored the buildup. Soon, the machine caught fire and was completely burned—losses of hundreds of thousands of USD.