A hydraulic guide rail lift should normally move smoothly and steadily during both lifting and lowering.
But what happens when a newly installed lift starts to shake or move in a "jerking" motion?
Recently, we worked with a customer who encountered exactly this problem with a double-rail, dual-cylinder hydraulic guide rail lift.
The platform was able to move up and down, but the movement was not smooth. During lifting, the platform would rise with noticeable vibration, moving upward in a repeated "jerk-pause-jerk" motion. The downward movement was also slightly uneven, although the shaking was less noticeable than during lifting.
At first, there were several possible causes.
After a step-by-step inspection, we eventually identified the real reason: air trapped inside the hydraulic cylinder and hydraulic lines.
Here is how we diagnosed and solved the problem.
1. The First Suspect: Guide Rails and Guide Rollers
Because this was a guide rail lift, our first suspicion was the mechanical guiding system.
If the guide rails or guide rollers have excessive friction, misalignment, damage, or insufficient lubrication, the platform can potentially move unevenly.
We therefore asked the customer to carefully inspect:
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The guide rails
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The guide rollers
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Roller rotation
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Possible scratches or abnormal wear on the rails
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Possible excessive friction between the rollers and rails
The customer also applied lubricant to the guide rails.
However, the problem remained.
There were no obvious scratches or abnormal marks on the guide rails, and the guide rollers were rotating freely.
This made it increasingly unlikely that the guide rail system was the main cause.
2. Checking the Safety Chain and Wire Rope
The next step was to eliminate another possible source of resistance.
The lift was equipped with a chain and a safety wire rope. We considered whether the safety wire rope might have been installed too tightly and was creating additional resistance during platform movement.
We asked the customer to loosen the safety wire rope and leave it only lightly engaged with the safety mechanism.
The customer confirmed that the safety rope itself was not carrying the platform load. Its purpose was safety protection rather than normal load bearing.
Even after adjusting it, the platform still moved with the same shaking motion.
So we could essentially rule out the safety wire rope as the cause.
3. Disconnecting the Mechanical Load From the Cylinders
At this point, we wanted to isolate the hydraulic system from the mechanical structure.
We asked the customer to disconnect the safety components and allow the hydraulic cylinders to operate separately.
Something important was immediately noticed.
When the cylinder was operated without the platform load, the cylinder produced a distinctive intermittent sound.
Instead of a completely smooth hydraulic movement, the cylinder made a repeated, segmented sound during movement.
This was an important clue.
The pump station itself sounded normal.
There was no obvious abnormal noise coming from the hydraulic power unit.
The unusual sound appeared to be coming from the cylinder.
So we continued investigating the hydraulic circuit.
4. Was the Hydraulic Pump Station the Problem?
At first, a hydraulic pump station problem was still possible.
A hydraulic power unit with unstable pressure, pump problems, valve problems, or other hydraulic abnormalities can sometimes cause uneven cylinder movement.
For a detailed look at how hydraulic valves control lift movement, see our article on Hydraulic Lift Solenoid Valve: Working Principle, Wiring, and Its Role in Lift Descent.
However, after listening carefully to the system, the pump station was operating normally.
The abnormal intermittent sound was associated with the cylinder movement rather than the pump station.
This changed our direction.
Instead of continuing to focus on the pump station, we began considering another possibility:
Could there be air trapped inside the hydraulic cylinder or hydraulic lines?
5. The Key Suspect: Trapped Air in the Hydraulic System
Hydraulic systems are designed to use hydraulic oil as the working medium.
Air, however, is compressible.
If air remains trapped inside a hydraulic cylinder or a relatively long hydraulic hose after installation, the oil flow may not produce completely stable cylinder movement.
The trapped air can compress and expand as hydraulic pressure changes.
This can result in:
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Jerky cylinder movement
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Platform vibration
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Uneven lifting
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Pulsating movement
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Intermittent cylinder noise
This possibility matched the customer's symptoms surprisingly well.
The fact that the lift was newly installed was also an important clue.
During installation, transportation, hose connection, and filling of the hydraulic system, some air can remain inside the hydraulic lines and cylinder.
This is especially worth checking on guide rail lifts where the hydraulic piping may be relatively long.
6. How We Removed the Air From the System
We asked the customer to perform a hydraulic bleeding procedure.
The basic process was as follows.
Step 1: Fully Lower the Cylinder
First, the cylinder was returned to its fully closed position.
This helped prepare the system for the bleeding process.
Step 2: Open the Manual Lowering Valve
The customer then opened the manual lowering valve on the hydraulic power unit.
The hydraulic oil was allowed to return through the hydraulic circuit.
The purpose was to help move trapped air and unstable oil flow out of the cylinder and hydraulic lines.
Step 3: Raise the Cylinder
After that, the cylinder was operated upward.
However, we did not require the cylinder to reach its maximum height.
Instead, it was raised to a position below the maximum stroke.
Step 4: Lower and Repeat
The cylinder was then returned downward.
This raising-and-lowering process was repeated approximately three to four times.
The objective was to allow the hydraulic oil to circulate through the cylinder and piping and gradually remove the trapped air.
7. Reconnecting the Platform and Bleeding the System Again
After the initial bleeding procedure, the cylinder was connected back to the platform.
We did not stop there.
Because the cylinder was now connected to the actual lifting structure, we asked the customer to repeat the raising and lowering process again.
The hydraulic system was cycled several more times to further remove any remaining air.
This second bleeding process was important because the hydraulic system was now operating under the actual mechanical conditions of the lift.
8. The Result: The Platform Movement Became Smooth
After the bleeding procedure was completed, the customer reported a significant improvement.
The previous shaking and jerking movement was essentially gone.
The platform could now move much more smoothly.
This allowed us to confirm the actual cause of the problem.
It was not:
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The guide rails
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The guide rollers
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The safety wire rope
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The chain
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The platform structure
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The hydraulic pump station
The main problem was air trapped inside the hydraulic cylinder and hydraulic lines.
9. What We Learned From This Troubleshooting Case
This case is a good reminder that troubleshooting a hydraulic lift should not focus on only one component.
When a newly installed hydraulic guide rail lift moves unevenly, it is easy to immediately suspect:
guide rails → rollers → mechanical structure → pump station → cylinder
But the hydraulic system itself should also be considered.
In particular, air in the hydraulic system should be one of the first things to check after installation, especially when:
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The lift is newly installed
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Hydraulic hoses are relatively long
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The hydraulic cylinder makes intermittent or unusual sounds
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The platform moves in a jerking motion
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The pump station sounds normal
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The guide rails and rollers appear to be working normally
10. A Practical Installation Tip for Hydraulic Guide Rail Lifts
For newly installed guide rail lifts, we recommend allowing sufficient time for the hydraulic system to be properly bled before judging whether the cylinder or pump station has a problem.
A simple approach is:
Cylinder fully down → allow oil to return → raise partially → lower → repeat 3–4 times → reconnect/operate the platform → repeat the bleeding cycle if necessary.
The exact bleeding procedure should always follow the lift's hydraulic system design and the manufacturer's instructions, with appropriate safety precautions.
If the platform continues to shake after proper bleeding, then other possible causes should be investigated, including guide alignment, roller adjustment, hydraulic valves, flow restrictions, cylinder synchronization, and mechanical resistance.
You may also find it useful to read about Remote Control for Hydraulic Lift Platforms: Convenience vs. Safety for a broader understanding of hydraulic lift control systems.
Conclusion
A shaking hydraulic guide rail lift does not necessarily mean that the cylinder, pump, or mechanical structure is defective.
In this real customer case, the solution was much simpler than we initially expected.
After checking the guide rails, guide rollers, safety wire rope, chain, platform, and hydraulic power unit, we eventually identified trapped air inside the hydraulic cylinder and hydraulic lines as the likely cause.
After bleeding the hydraulic system several times, the platform movement returned to normal.
This is why proper hydraulic bleeding after installation is an important step for hydraulic guide rail lifts, particularly systems with longer hydraulic piping.
If your hydraulic lift is moving up and down with a jerking or vibrating motion after installation, checking for trapped air in the hydraulic system is a good place to start.
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