Troubleshooting Kobelco SK135SR-2: Reverse Tracking Issue on One Side

[MikePhua]

The Kobelco SK135SR-2 is a versatile, compact excavator, known for its robust performance in tight spaces. However, like any machine, it can encounter issues that affect its functionality. One such problem is when the excavator experiences trouble tracking in reverse on one side, particularly after it warms up. This issue is not uncommon and can be traced back to several potential causes, which we will explore in detail here.
Understanding the Problem
The issue in question is that the Kobelco SK135SR-2 does not track properly when reversing on one side of the machine once it has warmed up. This malfunction can result in the machine not maintaining equal speeds on both tracks, which in turn can cause uneven wear, reduced maneuverability, and potential damage to the drivetrain.
Possible Causes and Troubleshooting Steps

1. Hydraulic Issues:
   • One of the most common causes of this tracking issue is related to the hydraulic system. If one side of the excavator is not moving correctly in reverse, it could be due to low hydraulic pressure or a failing hydraulic pump.
     
   • Possible Solutions:
     • Check the hydraulic fluid level to ensure it is within the recommended range.
       
     • Inspect the hydraulic pump for any signs of wear or damage, which could result in poor fluid pressure.
       
     • Look for leaks or blockages in the hydraulic lines leading to the problematic side of the machine.
       
2. Track Drive Motor Failure:
   • The track drive motor is responsible for converting hydraulic power into mechanical power that drives the tracks. If one motor is malfunctioning, it can cause the machine to struggle with tracking, especially in reverse.
     
   • Possible Solutions:
     • Inspect the track drive motor for any signs of damage or wear.
       
     • Perform a motor test to check for consistent operation between both sides.
       
     • If needed, replace the faulty track drive motor.
       
3. Electrical or Sensor Malfunctions:
   • Modern excavators like the Kobelco SK135SR-2 rely on various sensors and electrical components to regulate the hydraulic system and track motors. A malfunctioning sensor could be sending incorrect signals to the system, causing imbalances in power distribution.
     
   • Possible Solutions:
     • Inspect all electrical connections and wiring to ensure there are no loose connections or damaged wires.
       
     • Use diagnostic tools to check for any error codes or abnormal readings in the system.
       
     • If a sensor is identified as the issue, replace it with a genuine part from the manufacturer.
       
4. Track Tension and Alignment:
   • Improper track tension or alignment can also contribute to one side of the machine not tracking properly, especially when reversing. If the tracks are unevenly tensioned, they may not move evenly.
     
   • Possible Solutions:
     • Check the track tension on both sides to ensure they are even and within the manufacturer's specifications.
       
     • Inspect the tracks for any signs of damage or wear, as a damaged track could affect movement.
       
     • Adjust the tension as needed to ensure balanced operation.
       
5. Proportional Valve or Pilot Valve Failure:
   • The proportional valve controls the flow of hydraulic fluid to the track drive motors. If it is malfunctioning, it could prevent the correct amount of hydraulic fluid from reaching the motor on one side, leading to improper movement.
     
   • Possible Solutions:
     • Inspect the proportional valve for signs of wear or damage.
       
     • Check the pilot valve, which works in tandem with the proportional valve, to ensure it is functioning correctly.
       
     • If either valve is found to be faulty, replacing it may resolve the tracking issue.
       

Real-World Case Studies
In one instance, an operator of a Kobelco SK135SR-2 noticed that the excavator was tracking unevenly in reverse after a few hours of operation. Upon inspection, the hydraulic fluid was found to be at a lower than optimal level, which was causing the imbalance in pressure. After refilling the hydraulic fluid and performing a system purge, the issue was resolved. This is a reminder that even simple issues like fluid levels can cause significant operational problems.
Another example involved a construction site where a Kobelco SK135SR-2 was not tracking evenly in reverse due to a failing track drive motor. The motor had worn out over time, and the operator had not noticed the gradual decrease in performance. After replacing the motor, the excavator returned to full functionality.
Conclusion
While the reverse tracking issue on a Kobelco SK135SR-2 can be frustrating, it is not an insurmountable problem. By methodically checking the hydraulic system, track drive motors, electrical sensors, and track tension, you can identify and resolve the root cause. Regular maintenance, such as checking fluid levels and replacing worn parts, can also help prevent similar issues in the future. Whether you’re a seasoned operator or a maintenance technician, understanding these common problems and solutions will ensure that your excavator remains in peak condition for the long haul.