Hitachi EX200-3 Hydraulic System Pulsing Issue

[MikePhua]

The Hitachi EX200-3 hydraulic excavator is a widely used mid-sized machine known for its reliable performance and robust hydraulic system. However, occasional pulsing in the hydraulics may occur, affecting operational fluidity and precision. Understanding the potential causes and remedies is critical for maintaining optimal excavator performance.
Potential Causes of Hydraulic Pulsing

• Air in the Hydraulic System: Air trapped in hydraulic lines or components can cause pulsations or surges. This often occurs after maintenance or due to leaks allowing air ingress.
  
• Contamination: Dirt or water inside the hydraulic fluid affects valve operation and pump performance, leading to erratic pressure changes.
  
• Faulty Hydraulic Pump: Worn or malfunctioning pump components may cause inconsistent flow rates and pressure, thus pulsing.
  
• Relief Valve Issues: Relief valves stuck or improperly adjusted can cause pressure fluctuations.
  
• Control Valve Problems: Internal wear or contamination in the control valves affecting smooth spool movement.
  
• Low Fluid Levels or Incorrect Fluid Type: Inadequate or incorrect hydraulic fluid can compromise system stability.
  
• Temperature Extremes: Very cold or hot fluid changes viscosity and flow characteristics, causing pulsation.
  

Symptoms to Note

• Erratic or jerky movement of boom, arm, or bucket.
  
• Vibrations or “pulsing” felt in control levers.
  
• Noise or rough operation during hydraulic actuation.
  
• Delays or jumps in hydraulic response.
  

Diagnostic Approach

• Check hydraulic fluid level, quality, and temperature.
  
• Inspect system for possible air ingress points and tighten fittings.
  
• Flush hydraulic system and replace fluid to remove contamination.
  
• Perform pump pressure and flow tests to ascertain performance.
  
• Test control and relief valves for proper operation and internal leakage.
  
• Use diagnostic tools and manufacturer manuals for system troubleshooting.
  

Solutions and Repairs

• Bleed the hydraulic system carefully to expel trapped air.
  
• Replace hydraulic filters regularly to prevent contamination buildup.
  
• Repair or replace faulty pumps, valves, or hoses identified during testing.
  
• Adjust or service relief valves to factory specifications.
  
• Maintain correct fluid levels using manufacturer-recommended hydraulic oils.
  
• Monitor system temperature and allow warm-up during extreme cold.
  

Terminology

• Hydraulic Pulsing: Fluctuations in fluid pressure causing erratic actuator movement.
  
• Relief Valve: Pressure control device preventing overpressure in hydraulic circuits.
  
• Control Valve: Regulates fluid flow direction and volume to actuators.
  
• Bleeding: Removing air trapped within the hydraulic lines.
  
• Spool Movement: The action of the sliding valve elements controlling fluid flow paths.
  

Small Story
An operator of a Hitachi EX200-3 encountered uneven boom motions with noticeable pulsing during digging. Technicians found air trapped due to a loose hydraulic fitting and contaminated oil from delayed filter replacements. After tightening fittings, flushing oil, and replacing filters, the hydraulic system regained smooth and responsive operation, reducing operator fatigue and increasing productivity.
Summary List

• Hydraulic pulsing in Hitachi EX200-3 can be caused by air, contamination, pump or valve malfunctions.
  
• Check fluid level, quality, and temperature first.
  
• Bleed air from the system and replace contaminated fluids.
  
• Test pumps and valves for wear or damage.
  
• Repair or adjust relief valves to proper settings.
  
• Regular maintenance including filter replacement is key to prevention.
  
• Ensure correct hydraulic oil type and volume per manufacturer standards.
  

By systematically diagnosing and addressing hydraulic pulsing, operators can maintain the Hitachi EX200-3’s precision and efficiency, prolonging machine life and enhancing jobsite outcomes.