Temporary Hydraulic Loss on Kobelco 115SRDZ Excavator

[MikePhua]

Overview of the Kobelco 115SRDZ Excavator
The Kobelco 115SRDZ is a compact yet powerful hydraulic excavator weighing approximately 31,750 pounds, equipped with an 84-horsepower Isuzu A-4BG1T diesel engine. Specializing in tight jobsite maneuverability, the 115SRDZ features a minimal front and tail swing radius that allows operation in confined spaces where larger machines cannot operate effectively. Its hydraulic system is designed for high efficiency, with dual variable displacement pumps delivering up to 62.8 gallons per minute combined flow at a system pressure of 4,980 psi for boom, arm, bucket, and travel circuits. This model is known for its advanced Electronic Active Control System (E.A.C.S.) that optimizes hydraulic responses for precise control and productivity.
Understanding Temporary Hydraulic Loss
A temporary loss of hydraulics, specifically on the left side of a Kobelco 115SRDZ, may manifest as a sudden reduction in arm or track functions or intermittent operation of auxiliary hydraulic circuits. This issue can be triggered by multiple causes including:

• Hydraulic fluid contamination or aeration.
  
• Faulty or clogged hydraulic filters.
  
• Malfunctioning hydraulic pump or valve components.
  
• Electrical faults affecting solenoid valves.
  
• Excessive heat causing fluid viscosity changes or thermal shutdown features activating.
  

Such hydraulic interruptions can significantly impair machine operation, reduce efficiency, and in severe cases, render the excavator inoperable until resolved.
Diagnostic and Troubleshooting Steps
To address temporary hydraulic loss, technicians should systematically:

• Check hydraulic oil levels and quality; low or degraded oil is a common root cause.
  
• Inspect and replace hydraulic filters if clogged or contaminated.
  
• Monitor system pressures using appropriate gauges to detect pump or valve failures.
  
• Examine solenoid valve functions and electrical connections for proper timing and voltage.
  
• Review computer diagnostics from the Electronic Active Control System for fault codes.
  
• Assess fluid temperature to ensure it remains within the designed operating range.
  

Enhanced diagnostic tools accessible via onboard monitors have improved fault isolation, helping reduce machine downtime.
Maintenance Recommendations
Routine maintenance plays a vital role in preventing hydraulic issues:

• Maintain oil cleanliness with scheduled filter and fluid changes; manufacturers typically recommend changes every 1,000 hours or sooner under severe conditions.
  
• Use manufacturer-approved hydraulic fluids adhering to recommended viscosity and compatibility.
  
• Regularly calibrate and inspect hydraulic sensors and electrical connections.
  
• Monitor operating environment temperatures and use appropriate coolers/accessories during extreme heat.
  

Implementing a proactive hydraulic maintenance program reduces incidents of temporary loss and extends component life.
Real-World Scenario
A contractor operating a Kobelco 115SRDZ on an urban site experienced abrupt failure of left-side hydraulics mid-project. Initial observations excluded external leaks or mechanical damage. Diagnostics revealed elevated fluid temperature and a partially blocked return line causing pressure fluctuations. After flushing and replacing the hydraulic fluid and filters, and restoring proper cooling fan operation, normal hydraulic function resumed, minimizing project delays.
Glossary of Key Terms

• Hydraulic Pump: Device converting mechanical energy to fluid power, driving actuator movement.
  
• Solenoid Valve: Electromechanical valve controlling fluid flow in hydraulic circuits.
  
• Aeration: Entrapment of air bubbles in hydraulic fluid, reducing transmission efficiency.
  
• E.A.C.S. (Electronic Active Control System): Computerized system managing engine and hydraulic pump output for optimized performance.
  
• Viscosity: Fluid's resistance to flow, affected by temperature.
  

Conclusion
Temporary hydraulic loss in a Kobelco 115SRDZ demands prompt, precise diagnosis to maintain machine productivity and operational safety. By understanding the interplay of hydraulics, fluid condition, and electronic controls, operators and technicians can implement effective preventive and corrective measures. Through routine maintenance and diagnostics, such issues are manageable, extending the machine’s service life and reliability in varying work conditions.