Komatsu PC50UU-2 Hydraulic Problems Detailed Overview

[MikePhua]

The Komatsu PC50UU-2 is a compact hydraulic excavator known for its maneuverability, efficiency, and solid construction optimized for urban and confined space projects. Despite its reliability, like any hydraulic machine, it can encounter hydraulic system issues that influence performance and machine availability.
Hydraulic System Overview
The PC50UU-2 features Komatsu’s Closed Load Sensing System (CLSS) hydraulic circuit, designed to provide consistent power and speed for all machine movements, including simultaneous operations. Its hydraulic architecture consists of:

• Two variable displacement main pumps plus one gear pump supplying a combined maximum flow around 51 liters per minute each).
  
• Maximum hydraulic operating pressure of about 270 bar (27 MPa).
  
• Axial piston hydraulic motors for travel.
  
• Servo-proportionally controlled hydraulic valves governing boom, arm, bucket, blade, and swing functions.
  
• Auxiliary hydraulic circuits allow attachment operation (e.g., breakers, augers).
  

This advanced system aims for smooth, efficient movement control under varying load and engine speed conditions.
Common Hydraulic Problems Reported
Operators have encountered several hydraulic-related issues on the PC50UU-2, including:

• Loss or lag of hydraulic power in attachments or boom movements.
  
• Erratic hydraulic flow resulting in jerky or slow operation of boom, arm, or bucket.
  
• Overheating of hydraulic fluid under prolonged or heavy use.
  
• Pressure drops affecting travel speed or swing functions.
  
• Leaks in hydraulic lines, pumps, or cylinders leading to fluid loss and contamination risks.
  

Potential Causes

• Hydraulic fluid contamination or degradation reducing system efficiency.
  
• Worn or failing hydraulic pump components weakening pressure generation.
  
• Faulty or stuck servo-control valves affecting fluid distribution.
  
• Air entering the hydraulic system causing cavitation and inconsistent operation.
  
• Damaged or leaking hydraulic hoses, fittings, or seals resulting in pressure loss and leaks.
  
• Blockages in hydraulic filters or strainers restricting fluid flow.
  

Maintenance and Troubleshooting Recommendations

• Routinely check and replace hydraulic fluid following Komatsu's recommended service intervals to preserve fluid quality.
  
• Inspect and replace hydraulic filters regularly to prevent contaminants from circulating.
  
• Monitor operating temperatures and allow for cooling periods to prevent overheating.
  
• Perform leak inspections on hoses, cylinders, and fittings, repairing or replacing as necessary.
  
• Use manufacturer diagnostic tools to test hydraulic pump pressure and valve functionality.
  
• Ensure proper bleeding of the hydraulic system during repairs to avoid air pockets.
  
• Operators should be trained to recognize early signs of hydraulic decline such as sluggish movement or unusual noises.
  

Key Parameters

• Hydraulic fluid capacity: Approximately 55 liters (14.5 gallons).
  
• Hydraulic pressure rating: Around 270 bar (3,900 psi).
  
• Hydraulic pump flow: About 51 liters per minute per pump (two main pumps).
  
• Low ground pressure undercarriage: enhances machine stability without excessive soil compaction.
  

Terminology

• CLSS (Closed Load Sensing System): Hydraulic system that adjusts pump flow and pressure based on load demand for efficiency.
  
• Variable Displacement Pump: Adjustable pump that varies output flow depending on pressure requirements.
  
• Servo-Proportional Control Valve: A valve that precisely modulates hydraulic flow to actuators based on control inputs.
  
• Cavitation: Formation of vapor bubbles in fluid due to pressure drops, leading to potential damage and poor performance.
  
• Hydraulic Fluid Contamination: Presence of dirt, water, or air in fluid degrading system function.
  

A Small Story
A contractor using a Komatsu PC50UU-2 for urban excavation in tight city alleys noticed gradual sluggishness in boom operation and irregular swinging. Investigation revealed dirty hydraulic oil along with a partially clogged return line. After flushing the system, replacing filters, and topping off with fresh hydraulic fluid, the excavator returned to smooth operation, exemplifying how critical regular hydraulic maintenance is in compact, high-cycle machines.
Summary List

• PC50UU-2 uses Komatsu’s efficient CLSS hydraulic system.
  
• Two major variable displacement pumps deliver over 50 L/min flow each at 270 bar pressure.
  
• Common problems: loss of power, erratic motion, fluid overheating, leaks.
  
• Regular fluid, filter changes, and system bleeding are essential.
  
• Diagnostic tools key for pump and valve function tests.
  
• Training operators reduces damage risk and downtime.
  
• Hydraulic capacity: approx. 55 liters (14.5 gallons).
  

Prudent maintenance combined with early diagnostics can extend Komatsu PC50UU-2 hydraulic system life, ensuring continued high performance on demanding job sites.