Here are two suggestions for buying a used machine: first, buy from a dealer to avoid purchasing a refurbished unit. Second, pay attention to the following points when buying a used excavator:

　　1. Open the engine hood and check the exhaust pipe for signs of smoke. You can pull out the dipstick and check for smoke. Excessive smoke usually indicates that the piston rings need replacing, and a major engine overhaul may not be far off. Basic checks also include checking the coolant and engine oil, checking the degree of battery corrosion, and looking for obvious leaks around the engine. Oil leaks mean the entire oil circuit may be contaminated.

　　2. Pay attention to the condition of the bucket and make sure the piling, breaking, and travel devices are in good order. Another important part is the bucket cylinder connecting pins and bushings. Be sure to check the tightness of these areas. Many problems arise from neglect of maintenance and inspection.

　　When the user starts the machine and moves the bucket, stick, and boom, they may see the pins or cylinders moving, but the stick and bucket do not move. This is caused by looseness in the pins and bushings.

　　3. Another key point is to carefully inspect the connection between the boom and the excavator. If the connection under the boom is excessively worn, it may cause the entire machine to lose its value.

　　4. Checking the hydraulic cylinders and hoses is very important. The best case is that the chrome-plated surface of the hydraulic cylinder has no scratches, dents, or signs of oil leakage. If hydraulic oil seeps out, dust may have contaminated the hydraulic system. Also confirm that the cylinder wall is not damaged or dented. The gap between the cylinder and the wall is very small. As long as there is a foreign object in the pipeline, it will cause the cylinder to generate a large amount of metal debris due to wear during operation, which will remain in the hydraulic system.

　　5. Carefully check the excavator for cracks and welding marks not left during original manufacturing. These things indicate that the machine has been used excessively.

　　6. Pay special attention to excess steel plate repairs. A used machine may have some scratches and dents, but too many patches may mean the equipment has been used for a long time.

　　7. When checking the tracks and undercarriage, do not forget to check the oil level and cleanliness. This part is easily overlooked, and usually very little oil remains. If the oil level is already low and water or other substances enter, it will cause even greater trouble.

　　8. After the engine is warmed up, tilt the machine so that it stands on one track, then alternate standing on each track in turn. Note how many times this can be done within 30 or 60 seconds, then compare with the other track. Also check the slewing ring and slewing bearing. Under normal conditions, the upper structure should start slewing smoothly and stop accurately, with only slight or no deviation. For small excavators, the slewing ring and slewing bearing should have the same service life as the machine. Therefore, any problem in this area must be noted.

　　9. Check the air filter and all pipes and clamps. Even a little dust is enough to ruin the entire engine. Pay attention to accumulated dust or dirt at the terminals. Also check the fan to ensure the belt is tight. Check the radiator to ensure it is clean. Neglecting the cooling system and intake system may cause the engine to overheat, thereby shortening the machine's service life.