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Komatsu PC220 Series Background
The Komatsu PC220 LC-8 hydraulic excavator is part of Komatsu’s long-standing PC series, first introduced in the 1980s and refined through multiple generations. The LC-8 variant, launched in the mid-2000s, features a 6-cylinder Komatsu SAA6D102E engine producing around 165 hp, paired with a closed-center hydraulic system and electronically controlled travel motors. Designed for general earthmoving, quarrying, and infrastructure work, the PC220 series has sold tens of thousands of units globally, with strong adoption in North America, Southeast Asia, and Australia. Komatsu’s reputation for durability and parts support has kept these machines active well beyond their warranty cycles.
Terminology Note
Operators have reported a recurring issue on the PC220 LC-8 where the machine experiences brief interruptions in travel, described as a momentary brake application or drive loss. This occurs in all travel speeds—low, medium, and high—and is noticeable even when the tracks are lifted off the ground. The result is a jerky, uneven motion, particularly when climbing or descending slopes.
Probable Causes and Diagnostic Path
In Darwin, a contractor experienced similar symptoms on a smaller Kubota U55-3. The issue was traced to high pilot pressure causing joystick vibration, which activated boom functions and diverted flow from the travel motors. After adjusting pilot pressure and reinforcing joystick mounts, the problem was resolved. This case suggests that joystick stability and pilot signal integrity are critical even in larger machines like the PC220.
Preventive Maintenance Recommendations
The Komatsu PC220 LC-8’s travel interruption issue is often linked to pilot pressure instability and hydraulic signal interference. By stabilizing joystick inputs, inspecting brake valves, and adjusting pilot settings, operators can restore smooth travel and prevent jerky motion. With proper diagnostics and preventive care, the PC220 remains a reliable performer in demanding excavation environments.
The Komatsu PC220 LC-8 hydraulic excavator is part of Komatsu’s long-standing PC series, first introduced in the 1980s and refined through multiple generations. The LC-8 variant, launched in the mid-2000s, features a 6-cylinder Komatsu SAA6D102E engine producing around 165 hp, paired with a closed-center hydraulic system and electronically controlled travel motors. Designed for general earthmoving, quarrying, and infrastructure work, the PC220 series has sold tens of thousands of units globally, with strong adoption in North America, Southeast Asia, and Australia. Komatsu’s reputation for durability and parts support has kept these machines active well beyond their warranty cycles.
Terminology Note
- Travel Motor: A hydraulic motor that powers the tracks, allowing the excavator to move.
- Pilot Pressure: Low-pressure hydraulic signal used to control valves and actuators.
- Brake Valve: A hydraulic valve that applies or releases the travel brake based on pilot signal and load conditions.
Operators have reported a recurring issue on the PC220 LC-8 where the machine experiences brief interruptions in travel, described as a momentary brake application or drive loss. This occurs in all travel speeds—low, medium, and high—and is noticeable even when the tracks are lifted off the ground. The result is a jerky, uneven motion, particularly when climbing or descending slopes.
Probable Causes and Diagnostic Path
- Pilot Pressure Instability: Excessive pilot pressure can cause joystick vibrations, inadvertently triggering boom or arm functions. These unintended movements may momentarily divert hydraulic flow from the travel circuit, causing a brief loss of drive.
- Brake Valve Sensitivity: The travel brake valve may be overly sensitive to pressure fluctuations, especially if internal seals are worn or contaminated.
- Joystick Feedback Loop: Vibrations in the joystick can create a feedback loop where minor inputs activate auxiliary functions, disrupting travel flow.
- Hydraulic Flow Prioritization: In Komatsu’s load-sensing system, boom and arm movements can override travel flow under certain conditions, especially if pilot signals are unstable.
- Check Pilot Pressure Settings: Use a hydraulic test kit to measure pilot pressure at the joystick and valve block. Adjust to factory specifications, typically around 400 psi.
- Stabilize Joystick Inputs: Hold the travel sticks firmly and avoid resting hands lightly during movement. This reduces unintended signal fluctuations.
- Inspect Brake Valve Assembly: Remove and clean the brake valve. Check for debris, worn seals, or sticking spools. Replace components as needed.
- Update Control Software: If available, install the latest firmware for the machine’s electronic control module to improve signal filtering and valve response.
- Test in High Travel Mode: Some operators report smoother travel in high gear due to reduced hydraulic prioritization. Use this mode for diagnostic comparison.
In Darwin, a contractor experienced similar symptoms on a smaller Kubota U55-3. The issue was traced to high pilot pressure causing joystick vibration, which activated boom functions and diverted flow from the travel motors. After adjusting pilot pressure and reinforcing joystick mounts, the problem was resolved. This case suggests that joystick stability and pilot signal integrity are critical even in larger machines like the PC220.
Preventive Maintenance Recommendations
- Inspect pilot lines quarterly for leaks, abrasion, or loose fittings.
- Replace hydraulic filters every 500 hours to prevent contamination.
- Calibrate joystick sensors annually to maintain signal accuracy.
- Monitor travel performance during slope operations and log anomalies.
- Train operators to maintain steady hand pressure and avoid resting on controls.
The Komatsu PC220 LC-8’s travel interruption issue is often linked to pilot pressure instability and hydraulic signal interference. By stabilizing joystick inputs, inspecting brake valves, and adjusting pilot settings, operators can restore smooth travel and prevent jerky motion. With proper diagnostics and preventive care, the PC220 remains a reliable performer in demanding excavation environments.
