08-15-2025, 10:56 PM
The Hitachi EX120-3 excavator is a versatile mid-sized machine widely used in construction and earthmoving, powered by an 81-horsepower engine and equipped with an advanced hydraulic system. One common challenge faced by operators is hydraulic pump flow control problems, which can impair machine performance and productivity.
Typical Symptoms of Flow Control Issues
Operators report that maintaining hydraulic oil within the specified temperature range and switching between “Power” and “General Purpose” work modes optimize pump behavior. Regular preventive maintenance and early component replacement greatly reduce downtime due to flow control failures.
Summary
Hydraulic pump flow control issues in the Hitachi EX120-3 excavator typically stem from component wear, fluid contamination, valve malfunctions, or elevated temperatures. Proper diagnosis involves monitoring pump performance, temperature, and conducting cycle time tests. Timely fluid maintenance, air bleeding, and professional pump servicing restore system efficiency and ensure reliable machine operation on diverse job sites.
Typical Symptoms of Flow Control Issues
- Reduced hydraulic flow affecting boom, arm, and bucket movements.
- Erratic or sluggish hydraulic responses during operation.
- Difficulty maintaining consistent hydraulic pressure especially under varying workloads.
- Unusual noises such as whining or chattering from the hydraulic pump area.
- Increased cycle times for boom and bucket actions, reducing efficiency.
- Wear or damage to the variable displacement hydraulic pump’s internal components, including valve plates, rotating groups, or shafts.
- Contamination from fluid debris or degraded hydraulic oil causing valve sticking or internal leakage.
- Malfunctioning flow control valves or pressure compensators disrupting proper pump displacement.
- Incorrect hydraulic fluid type or oil degradation affecting viscosity and flow characteristics.
- Air entrainment due to leaks or improper bleeding reduces pump efficiency.
- Electrical or sensor faults impacting flow control signals or feedback.
- Measure hydraulic oil temperature, which should be maintained near 50-55°C (122-131°F) for optimal pump operation.
- Observe the operation modes such as “Power Mode” and “Work Mode” to verify control settings.
- Conduct cycle time tests for boom, arm, and bucket cylinders to detect sluggish movements.
- Inspect and replace worn pump parts including rotating groups, valve plates, and seals.
- Change hydraulic fluid and filters regularly to prevent contamination buildup.
- Bleed the hydraulic system thoroughly to remove trapped air.
- Engage experienced technicians and consider professional pump rebuilds for extensive wear.
- Variable Displacement Pump: A hydraulic pump whose output flow can be adjusted to match system demand.
- Flow Control Valve: Regulates the fluid flow rate to various hydraulic functions.
- Valve Plate: A critical component directing fluid within the pump.
- Rotating Group: Includes pistons and cylinder blocks converting mechanical energy to fluid flow.
- Air Entrainment: Presence of air bubbles in hydraulic fluid which degrade performance.
Operators report that maintaining hydraulic oil within the specified temperature range and switching between “Power” and “General Purpose” work modes optimize pump behavior. Regular preventive maintenance and early component replacement greatly reduce downtime due to flow control failures.
Summary
Hydraulic pump flow control issues in the Hitachi EX120-3 excavator typically stem from component wear, fluid contamination, valve malfunctions, or elevated temperatures. Proper diagnosis involves monitoring pump performance, temperature, and conducting cycle time tests. Timely fluid maintenance, air bleeding, and professional pump servicing restore system efficiency and ensure reliable machine operation on diverse job sites.
