Common Troubleshooting Methods for Hydraulic Power Units

Common Troubleshooting Methods for Hydraulic Power Units

Hydraulic power units (also known as hydraulic power packs or HPUs) are the core power source for hydraulic systems widely used in lifting platforms, trailers, marine hatches, dam gates, agricultural machinery and engineering equipment. Even high-quality hydraulic power units may develop faults after long hours of continuous operation. Fast and correct hydraulic troubleshooting reduces machine downtime and avoids expensive secondary damage to hydraulic pumps, solenoid valves and seals.

This guide shares practical, field-proven troubleshooting methods for the most frequent hydraulic power unit failures. If you cannot solve the problem after inspection, or you need a replacement hydraulic power pack or custom hydraulic power unit for your project, feel free to send us an inquiry.

Basic Safety Rule Before Troubleshooting

Always cut off power and release residual hydraulic pressure before checking any hydraulic power unit. Do not touch hot hydraulic oil or pressurized pipelines. Prepare pressure gauges, multimeters and clean tools for inspection.

1. Hydraulic Power Unit Cannot Build Pressure / Pressure Loss

Symptom: Motor runs normally, but the actuator cannot lift loads or pressure cannot reach the set value. Common causes:

• Relief valve stuck, dirty or misadjusted

• Internal leakage of the hydraulic pump

• Damaged seals and internal leakage inside valve blocks

• Blocked suction filter or insufficient hydraulic oil

• Solenoid valve spool stuck, coil voltage abnormal

Troubleshooting steps:

1. Check hydraulic oil level and oil contamination

2. Test relief valve setting and clean the valve core

3. Check the suction filter and suction pipe for air intake

4. Measure voltage of the solenoid coil

5. Inspect pump wear condition

2. Hydraulic Power Unit Overheating

Symptom: Hydraulic oil temperature rises quickly, oil becomes thin, the unit loses efficiency, and seals age rapidly. Common causes:

• Continuous overflow of relief valve

• Clogged oil cooler or poor heat dissipation

• Wrong hydraulic oil viscosity grade

• Long-time overload operation

• Internal leakage inside pump or manifold block

Troubleshooting steps:

1. Check whether the relief valve keeps bypassing under no load

2. Clean the cooling system and heat exchanger

3. Check oil quality and replace contaminated hydraulic fluid

4. Confirm the working load matches the rated parameter of your hydraulic power pack

3. Abnormal Noise & Cavitation

Symptom: HPU makes knocking, hissing or grinding noise when working. Common causes:

• Air enters the suction line

• Suction strainer blocked

• Hydraulic oil viscosity too high at low temperature

• Pump bearing wear or damaged internal parts

• Loose mounting bolts

Troubleshooting steps:

1. Check suction pipe joints for air leakage

2. Bleed air from the hydraulic system

3. Clean or replace suction filter

4. Check oil temperature and oil grade

5. Inspect pump installation and fasteners

4. Hydraulic Oil Leakage

Symptom: Oil seeps from pipe joints, valve surfaces, motor shaft or cylinder connections. Common causes:

• Aging, cracked or wrong-size O-rings and seals

• Loose fittings and hydraulic hose connections

• Rough sealing surface on manifold

• Excessive working pressure exceeding seal rating

Troubleshooting steps:

1. Find external leak points and retighten fittings

2. Replace worn seals with matched hydraulic sealing parts

3. Check whether working pressure exceeds the unit rating

4. Inspect manifold surface for scratches

5. Slow Actuator Movement

Symptom: The cylinder runs slowly under normal pressure. Common causes:

• Clogged return filter

• Flow control valve misadjusted

• Worn hydraulic pump with insufficient flow output

• Internal leakage inside cylinder or valve

• Low voltage supply for DC hydraulic power unit

Troubleshooting steps:

1. Check filter condition and oil cleanliness

2. Readjust flow control valve

3. Test pump flow performance

4. For DC hydraulic power packs, verify stable voltage under load

6. Motor Does Not Start

Symptom: No action when turning on the power. Common causes:

• Power failure, blown fuse or poor wiring contact

• Overload protection triggered

• Damaged motor or relay

• Control switch failure

Troubleshooting steps:

1. Check power supply and circuit

2. Reset overload protection

3. Test relay and control switch

4. Inspect motor winding

Preventive Maintenance Tips for Hydraulic Power Packs

Most hydraulic faults come from oil contamination. Follow these routines to extend HPU service life:

• Replace hydraulic oil and filters periodically

• Keep the oil tank sealed and prevent water and dust entering

• Check seal condition regularly

• Do not modify the relief valve pressure randomly

• Choose matched hydraulic power unit models according to your working pressure, flow and application environment

Need a New or Custom Hydraulic Power Unit?

If your old hydraulic power pack suffers repeated breakdowns, or you are sourcing a reliable hydraulic power unit for trailers, marine systems, dam gates, lifting equipment and special machinery, we manufacture standard and custom HPUs, including mini hydraulic power units, single-acting & double-acting hydraulic power packs, AC and DC hydraulic power units.

Send your technical requirements: working pressure, flow rate, voltage, mounting size and application scenario. We will reply with a quotation and technical drawing quickly.

Contact us for your hydraulic power unit solution now.