This will be the last post in this series, but I want to talk about a few cases where improper maintenance and care actually caused failures, so that friends in this field can avoid the traps and reduce trouble in the future.

Once again, I must emphasize:
Always pay attention to machine maintenance and inspection! Perform the pre-shift checks as required. Nowadays, it’s already hard to find skilled operators. Whether you’re a substitute or the main operator, if you take good care of the machine, you’ll be considered an excellent operator, and it will be easier for you to find work. But if you treat a machine like it’s just returned from World War II, few people would want to hire you. Even if you bought the machine yourself, no matter how good it is, it will constantly have problems if abused!

For example, when cracks appear on booms or arms, I won’t discuss operation errors here—but if you never do your pre-shift inspections, that’s a big mistake! No machine’s boom or arm will suddenly break under normal use—it always starts with small cracks that expand until final breakage (unless you’re doing circus stunts with it). That’s why I never side with people who complain about “poor quality” in forums. If you spot cracks and keep using the machine without reporting them to the owner, who would ever say, “just keep using it until it breaks”?

Another example: when the front-end pinhole of a boom tears off, people blame it on poor quality. But there are many causes for such failures, and they all share patterns—these belong in the scope of maintenance, so I won’t expand too much here.

Now, let’s discuss problems caused by improper maintenance so everyone can avoid them:

1. Do not blindly extend engine oil replacement intervals.

Especially without monitoring the oil’s condition. The manufacturer’s interval only ensures safe use. Extending beyond that without evidence is harmful, unless you don’t care about the machine’s life. Oil’s effectiveness depends mainly on additives, which can’t be judged simply by viscosity or feel.

A practical tip: When changing oil at the recommended interval, check the engine’s rocker arms. If you don’t see sludge deposits, that oil is suitable, and you might try carefully extending intervals until sludge appears—then stop. This method has been proven in practice. It costs nothing, only careful observation.

2. Do not blindly add more fuel filters.

Each fuel filter’s efficiency is measured under its designed flow resistance. Adding more filters only increases resistance, reduces fuel flow, and raises costs. Manufacturers design fuel systems with strict standards already. Many cases in the field show that extra filters with insufficient capacity quickly clog, leaving filters half-filled and engines underpowered.

3. Do not leave makeshift filters (like nylon stockings) in the fuel filler.

It’s fine to use them to catch debris during refueling, but remove them immediately afterward. Leaving them blocks the tank venting. As fuel level drops, vacuum pressure increases, starving the engine. (Most CAT fuel tank caps have a built-in air filter element, which needs maintenance and isn’t cheap. Tanks run under negative pressure during operation—this is often overlooked.)
Also, when cleaning fuel lines, mark them. Mistakes in reconnecting in/outlet lines can cause serious failures.

4. Do not use 68# hydraulic oil blindly.

Especially not in variable displacement piston pumps. Using oil that’s too viscous causes cavitation at cold start, enlarging slipper clearances—not a quality issue but wrong oil use. Even in warm climates like Hainan, it’s problematic. In cold regions (like Jilin), I’ve seen CAT 988G and CAT 6090B suffer severe cavitation because of intermittent operation. They had to build semi-underground garages for overnight parking to keep warm, and still used only factory 10# oil. If you try compensating worn pumps with thicker oil, the result will only be worse.

5. Do not operate machines in water deeper than the track height.

If unavoidable, check the swing bearing’s grease pan immediately afterward for water contamination, and replace grease if needed. Most swing bearings fail this way. Remember: excavators are not submarines. Some brands even have open grease pans, so muddy water can easily enter. Don’t be proud showing off videos of “deep water” work—it only leads to costly failures.

6. Always replace swing and travel gearbox oil on time (or earlier).

Even using regular quality oils (like Changcheng brand) is fine—don’t extend intervals carelessly. Small machines especially suffer, with gearbox oil often turning rancid. No need for expensive hypoid gear oils unless specified. Timely replacement is the key.

7. Wheel loader transmission oil and cooling system must be maintained.

Use 16# oil in summer, 8# in winter (unless otherwise specified). Never run under overheating. Don’t waste money on unknown imported oils. For wheel loader axles (spiral gear), GL-3 or GL-4 oil is enough—higher grade hypoid oil is unnecessary and only raises cost. For brake fluid, upgrade one grade higher to improve boiling point and prevent brake failure. Bulldozers (hydrodynamic or hydrostatic) must follow manual specifications strictly. Hydrostatic systems are especially sensitive—wrong oil leads to massive and unaffordable repairs.

8. Undercarriage machines are not meant for long-distance travel.

Use trailers for transport, not only for speed but to reduce wear on undercarriage components. Chains of poor quality accelerate wear on sprockets, rollers, and idlers, forcing early replacement of the entire set. Don’t try to “save” small transport costs and end up with major undercarriage expenses.

9. Use aftermarket parts wisely.

They reduce costs, but not all parts are suitable. Even bucket teeth and bushings must be checked carefully. Many cases of lost bucket teeth are due to poor precision: teeth don’t seat properly on adapters, relying only on pins, leading to lost or broken parts.
Filters, however, should always be OEM or top-brand. I know of excavators running over 32,000 hours in lime mines, never once repairing electronic fuel systems—all because they consistently used OEM filters and changed them on time. That’s in Shandong, Zaozhuang, Shanting.

In summary:
I only hope everyone realizes that money is hard-earned. Don’t let negligence in maintenance lead to huge repair costs. Spend on preventive maintenance, not on repairs—the latter is far more expensive.

And remember: there is no such thing as a machine that becomes better after being repaired. Nowhere in the world can a repair shop fully restore a machine to factory standard. At best, it will just “get by.”