October 29, 2026
Hydraulic power units are essential to the operation of many automotive lifts, providing the pressure needed to raise and lower vehicles safely and efficiently. When a hydraulic power unit isn’t working properly, it can interrupt shop operations, reduce lifting performance, and lead to unnecessary downtime.
Fortunately, many common hydraulic power unit problems can be traced to issues with electrical connections, hydraulic fluid, valves, or other components. Understanding what to look for can help you identify potential causes and determine when maintenance or replacement parts may be needed.
Below are some common hydraulic power unit problems, possible causes, and troubleshooting tips to help get your equipment back in working order.
1. Hydraulic Power Unit Motor Won’t Run
If your hydraulic power unit motor won’t start, the problem may be related to the electrical supply, wiring, or the motor itself.
Possible causes include:
- Blown fuse or tripped circuit breaker
- Burned-out start switch
- Damaged or burned-out motor
- Incorrect motor wiring
- Incorrect supply voltage or frequency
Troubleshooting Tips:
Start by checking the electrical supply. Verify that the incoming voltage matches the specifications on the motor nameplate and inspect the circuit breaker or fuse.
Incorrect wiring can also prevent the motor from operating. Have a qualified technician compare the motor connections with the electrical schematic provided in the equipment’s installation manual.
Avoid using extension cords whenever possible, as voltage drops can affect motor performance. If the electrical supply and wiring are correct but the motor still won’t operate, the start switch or motor may need further evaluation or replacement.
2. Hydraulic Lift Won’t Raise or Operate Under Load
A hydraulic power unit may run normally but fail to raise the lift or struggle when lifting a vehicle. This can indicate that the hydraulic system isn’t developing or maintaining sufficient pressure.
Possible causes include:
- Air trapped in the hydraulic fluid
- Low hydraulic fluid level
- Binding or internally leaking hydraulic cylinders
- Leaking release or relief valve
- Damaged hydraulic pump
- Pump failing to prime
- Incorrect motor rotation or supply voltage
- Excessive load or incorrect relief pressure
Troubleshooting Tips:
Begin by checking the hydraulic fluid level according to the equipment manufacturer’s instructions. Low fluid levels can introduce air into the system and prevent the pump from operating effectively.
If air is present, the hydraulic cylinders may need to be bled using the procedures outlined in the lift’s installation manual.
Also inspect the system for signs of contaminated hydraulic fluid, damaged seals, or valve problems. Contamination can interfere with valve operation and reduce hydraulic performance.
If the unit operates normally without a load but struggles when lifting, verify that the vehicle’s weight does not exceed the lift’s rated capacity.
Persistent lifting problems may indicate a damaged pump, internal cylinder leakage, or a valve that requires professional inspection or replacement.
3. Hydraulic Power Unit Won’t Hold Pressure
A hydraulic lift that gradually loses pressure or fails to maintain its raised position may have an internal hydraulic leak or a valve that isn’t sealing properly.
Possible causes include:
- Contaminated hydraulic fluid
- Leaking check valve
- Leaking release valve
- Leaking relief valve
- Internal hydraulic cylinder leakage
Troubleshooting Tips:
Check for signs of contaminated hydraulic fluid and inspect the system for visible leaks.
The check valve plays an important role in maintaining hydraulic pressure when the power unit is off. Dirt or debris can prevent the valve from sealing correctly, allowing pressure to escape.
The release and relief valves should also be evaluated for contamination, wear, or damage.
If the valves appear to be functioning correctly, internal cylinder leakage may be responsible for the pressure loss.
Because unexpected pressure loss can create a serious safety hazard, remove the lift from service until the problem has been properly diagnosed and corrected.
4. Hydraulic Lift Lowers Slowly or Won’t Lower
When a hydraulic lift lowers more slowly than normal or won’t lower at all, the problem may involve the release valve, hydraulic cylinders, or electrical components controlling pressure release.
Possible causes include:
- Binding hydraulic cylinder
- Clogged release valve
- Inoperable solenoid coil
Troubleshooting Tips:
Inspect the release valve for possible contamination or restrictions that could interfere with hydraulic fluid flow.
Contaminated hydraulic oil may need to be replaced, and affected components may require cleaning or servicing according to the manufacturer’s instructions.
For power units equipped with an electrically operated release valve, a faulty solenoid coil may prevent the valve from operating correctly.
Cylinder binding can also restrict movement and should be evaluated using the lift’s installation and service instructions.
If the lift remains raised and will not lower, do not attempt to force movement or bypass the equipment’s safety systems. Have a qualified service technician diagnose the problem.
5. Hydraulic Power Unit Is Leaking Oil
Hydraulic oil leaks can affect system performance, create workplace hazards, and potentially damage equipment if left unaddressed.
Possible causes include:
- Clogged reservoir breather
- Loose pipe plugs
- Loose reservoir or tank connections
- Overfilled hydraulic reservoir
- Loose hoses or fittings
Troubleshooting Tips:
Begin with a visual inspection to identify where the hydraulic fluid is escaping.
Check the reservoir, breather, pipe plugs, hoses, and fittings for visible signs of leakage or damage.
An overfilled reservoir can also contribute to oil leakage. Verify that the fluid level is correct for the specific power unit and lift configuration.
Loose fittings or connections may require tightening to the torque specifications listed in the equipment’s installation manual. Damaged seals, hoses, or other components should be replaced as needed.
Never inspect a suspected high-pressure hydraulic leak with your hands. Hydraulic fluid under pressure can penetrate the skin and cause serious injury.
6. Hydraulic Power Unit Makes Unusual Noises
Unusual sounds coming from a hydraulic power unit can indicate problems with the motor, pump, hydraulic fluid, or mounting components.
Possible causes include:
- Air in the hydraulic fluid
- Low hydraulic fluid level
- Overloaded lift
- Damaged hydraulic pump
- Pump failing to prime
- Worn or damaged motor
- Loose motor mounting bolts
- Incorrect motor voltage or wiring
Troubleshooting Tips:
Start by checking the hydraulic fluid level and looking for conditions that could allow air to enter the system.
Inspect the inlet tubing and associated connections for looseness or damage. Air entering the hydraulic system can interfere with pump operation and contribute to unusual noises.
If the noise occurs primarily while lifting a vehicle, confirm that the load is within the lift’s rated capacity.
Loose motor mounting bolts can also create excessive vibration or rattling. Check mounting hardware and have any loose fasteners tightened to the specified torque.
If the noise continues, the motor or hydraulic pump may be damaged and require further evaluation.
Preventing Common Hydraulic Power Unit Problems
Proper hydraulic system maintenance goes beyond checking fluid levels and inspecting individual components. Regularly servicing your entire lift can help identify potential problems before they lead to equipment failure. A few important maintenance practices include:
- Check hydraulic fluid levels. Maintain the proper fluid level and use the hydraulic oil specified for your equipment.
- Keep hydraulic fluid clean. Contamination can damage internal components and interfere with valve operation.
- Inspect hoses and fittings. Look for leaks, loose connections, and signs of wear.
- Monitor lift performance. Address unusual noises, slow lifting, and inconsistent movement before problems become more serious.
- Check electrical components. Make sure switches, wiring, and electrical connections are in good condition.
- Follow recommended maintenance procedures. Refer to the equipment’s installation and service manuals for inspection intervals and maintenance requirements.
Routine maintenance helps identify developing problems early and can reduce the likelihood of costly repairs or extended downtime. For additional maintenance recommendations, read SVI’s Hydraulic Equipment Care for Car and Truck Lifts.
Additional Hydraulic Power Unit Troubleshooting Resources
While these tips cover many common hydraulic power unit problems, some issues require more detailed inspection or component-level troubleshooting.
For additional technical information, including hydraulic valve diagrams, component identification, recommended torque specifications, and other service references, consult the Complete Hydraulic Power Unit Troubleshooting Guide (PDF).
This article is intended as a general troubleshooting reference and does not replace the equipment manufacturer’s operating, installation, or service instructions. Hydraulic lift repairs should be performed by qualified personnel following appropriate safety procedures.
Find Hydraulic Power Units and Replacement Parts at SVI
When troubleshooting reveals a worn or damaged component, finding the right replacement part is an important step toward getting your equipment back in service.
SVI International offers a wide selection of power units and replacement components for automotive lifts, including motors, pumps, valves, reservoirs, seals, and other hydraulic system parts.
Whether you need a replacement component or an entire hydraulic power unit, SVI can help you identify parts that meet your equipment’s requirements.
Contact SVI International at 800-321-8173 for assistance with hydraulic power units and replacement parts.