John Deere 120C Excavator Troubleshooting and Maintenance

[MikePhua]

The John Deere 120C is a popular model in the construction industry, known for its versatility and robust performance in a variety of applications, including excavation, lifting, and material handling. As with any heavy equipment, proper maintenance is essential to ensuring the machine's longevity and optimal performance. However, like all machines, the 120C can experience issues that may hinder its operation. This article will explore some common problems with the John Deere 120C excavator, particularly focusing on troubleshooting, maintenance, and solutions for various malfunctions.
Overview of the John Deere 120C
The John Deere 120C is a hydraulic excavator designed for medium to heavy-duty tasks. With a powerful engine and durable hydraulic systems, the 120C is designed for digging, grading, and lifting in various environments. It is widely used in both commercial construction and municipal infrastructure projects, thanks to its efficiency and reliability.
Common Problems with the John Deere 120C
Although the John Deere 120C is a reliable piece of machinery, like any heavy equipment, it is susceptible to wear and tear over time. Several issues can affect its operation, especially if the excavator is not regularly serviced or used under extreme conditions. Here are some of the most common problems faced by owners and operators of the 120C.
1. Hydraulic System Failures
Hydraulic problems are some of the most common issues reported with the John Deere 120C. Since the machine relies heavily on hydraulics for its boom, arm, and bucket movements, any failure within the system can cause significant operational disruptions. The most common hydraulic issues include:

• Low Hydraulic Pressure: This can cause slow or unresponsive movements in the boom, arm, or bucket. It is often due to low hydraulic fluid levels, a clogged filter, or worn hydraulic components.
  
• Hydraulic Leaks: Leaks in hoses, fittings, or the hydraulic pump can lead to a loss of pressure, making the machine less efficient and sometimes completely inoperable. Leaks can also lead to contamination of hydraulic fluid, which can damage the entire system.
  
• Worn Hydraulic Pump: Over time, the hydraulic pump can wear out, reducing its ability to generate the necessary pressure. This could cause intermittent failures in the hydraulic system or a complete loss of function in certain parts of the machine.
  

To diagnose hydraulic issues, operators should inspect the hydraulic fluid level, check for leaks, and examine the hydraulic pump and hoses for signs of damage or wear.
2. Electrical System Malfunctions
The John Deere 120C features an advanced electronic system that controls various aspects of the machine, from the engine to the hydraulics. Issues with the electrical system can result in loss of power, erratic behavior, or failure to start. Common electrical issues include:

• Faulty Sensors: The 120C is equipped with several sensors that monitor various systems, such as engine temperature, hydraulic pressure, and fuel levels. If these sensors malfunction or send incorrect signals to the control system, the machine may experience errors, including warning lights or failure to operate correctly.
  
• Battery or Charging System Problems: A dead battery or a malfunctioning alternator can cause the machine to fail to start or lose power during operation. If the alternator is not charging the battery properly, the electrical system will not function as expected.
  
• Loose or Corroded Wiring: Over time, the wiring in the electrical system can degrade, leading to loose connections, short circuits, or complete failure of certain systems. Corroded battery terminals or connectors can prevent the machine from starting or operating smoothly.
  

Inspecting the electrical system involves checking the battery voltage, ensuring the charging system is functioning, and inspecting the wiring and sensors for signs of damage or wear.
3. Engine Performance Issues
The engine is the heart of any excavator, and issues here can result in a significant loss of performance. The John Deere 120C’s engine, if not properly maintained, can suffer from a range of problems, including:

• Overheating: The engine may overheat due to a clogged radiator, insufficient coolant, or a malfunctioning thermostat. Overheating can cause severe damage to engine components if not addressed promptly.
  
• Low Power: If the engine is underperforming, it could be due to a clogged fuel filter, dirty air filter, or issues with the fuel injectors. Low power output can affect the excavator’s ability to lift heavy loads or perform difficult tasks.
  
• Engine Misfire or Rough Idle: A misfiring engine can be caused by faulty spark plugs, bad fuel, or issues with the ignition system. This can lead to rough idling, poor fuel efficiency, or even complete engine failure.
  

Regular oil changes, filter replacements, and coolant checks can help prevent many of these engine-related problems.
4. Track and Undercarriage Wear
The undercarriage of an excavator takes a lot of abuse, particularly in rough terrain. The John Deere 120C features a robust undercarriage, but wear and tear over time can cause significant issues. Common problems in the undercarriage include:

• Track Tension: If the tracks are too loose or too tight, it can cause excessive wear on the rollers and sprockets, leading to faster deterioration and the need for more frequent repairs.
  
• Worn Rollers and Idlers: Over time, the rollers and idlers that support the tracks can wear out, making it harder for the excavator to move efficiently.
  
• Track Misalignment: Misaligned tracks can cause uneven wear and decrease the efficiency of the machine. Misalignment may be due to damaged components or improper maintenance.
  

Routine inspection of the tracks, rollers, and undercarriage components is essential for ensuring smooth operation. Keeping the tracks properly tensioned and replacing worn components can prolong the life of the excavator.
5. Uneven or Poor Digging Performance
Occasionally, the John Deere 120C may struggle with digging performance, especially when working in tough soil conditions or with heavy loads. The most common causes of this issue are:

• Hydraulic System Failure: As mentioned earlier, a malfunctioning hydraulic system can cause poor digging performance due to insufficient pressure or fluid.
  
• Worn Bucket Teeth: Over time, the teeth on the excavator’s bucket will wear down, reducing their effectiveness at digging and breaking up soil.
  
• Imbalanced or Improperly Loaded Bucket: If the bucket is overloaded or not properly balanced, it may struggle to dig efficiently or may result in premature wear.
  

Ensuring the bucket is in good condition and that the hydraulic system is functioning correctly can help maintain optimal digging performance.
Preventative Maintenance Tips for the John Deere 120C
To avoid many of the common issues discussed above, regular maintenance is key. Here are some preventative maintenance tips for the John Deere 120C:

• Regularly check hydraulic fluid levels and inspect for leaks.
  
• Replace filters (engine oil, hydraulic, and fuel filters) on schedule.
  
• Inspect the battery and electrical system for proper function and corrosion.
  
• Clean the engine cooling system and monitor coolant levels.
  
• Inspect the undercarriage regularly for wear, misalignment, and track tension.
  
• Lubricate all moving parts as per the maintenance schedule.
  

By adhering to the manufacturer’s recommended maintenance schedule and addressing issues as they arise, operators can extend the lifespan of their John Deere 120C excavators and maintain high productivity on job sites.
Conclusion
The John Deere 120C excavator is a robust and reliable machine, but like all heavy equipment, it requires regular maintenance and occasional troubleshooting. By understanding the common issues that affect the 120C and knowing how to address them, operators can ensure that the machine remains in good working order, minimizing downtime and maximizing productivity. Whether it’s hydraulic issues, engine performance problems, or track wear, proactive maintenance and timely repairs are the keys to keeping the John Deere 120C running smoothly.