Causes and Troubleshooting of Squealing Hydraulic Cylinders

Blog | October 14th, 2016

The high-pitched mechanical tones of a tortured hydraulic system are often traced back to squealing hydraulic cylinders. A regimented troubleshooting procedure then makes haste to eliminate the noisome wail and determine whether more is going on here. Ask the right questions before jumping in, though, and avoid an unproductive repair experience. Does the squealing happen at all flow rates? Is stroke speed contributing to the problem? It’s this process of elimination that will get the gear mobile again, so let’s get our own system-diagnosing brains moving.

What Causes Hydraulic Cylinder Squeal? 

Aeration is a common factor in this situation. Aeration is simply a leak, one that usually occurs on the suction side of the mechanism. The resulting leak causes an erratic whine or squealing noise to propagate along the frame of the mobile gear, but it usually tracks back to the cylinder. Of course, as with any diligent system analysis process, the initial cause doesn’t always bring the story to a fast end. There’s the cause of the aeration to discover. Again, it’s a Sherlockian process of elimination that works best. Replace parts if necessary, but begin with cheaper replacements. The rod and piston seals make a fine start point, but this issue may not even be a mechanical problem, so what ails the cylinder?

Assessing Other Causative Factors 

If the cylinder is tested and found to be in optimal working condition, then what about checking the oil? Hydraulic fluid is vulnerable to atmospheric contamination, so a potential leak may originate at another point on the system but be carried into the cylinder. The oil foams or takes on the consistency of a soapy scum. The cylinder compresses, as it should, but the typically non-compressible oil squeezes the tiny air bubbles until they heat and release energy as that alarming shriek. Corrective actions at this point suggest an initial look at the oil, followed by an inspection of the couplings that hook the cylinder to the mobile vehicle. Now, if these tests don’t yield fruit, then and only then is it time to cause a stoppage by taking the cylinder back to the bench for further testing.

There’s a law that engineers find very useful when a troubleshooting protocol is active. It’s called Occam’s Razor. Basically, it states that the simplest answer is usually the correct one, so begin with obvious problems before making an impulsive decision to disassemble a squealing hydraulic cylinder. Look for aeration in the oil before replacing seals or the entire unit.

Mobile Hydraulic Specialties Pty Ltd

Factory 89, 38-40 Popes Road
Keysborough, Victoria, 3173

Phone: (03) 9798-6511

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