Why is My Hydraulic Pump Making Unusual Noises?

Not all hydraulic pump noises are worth worrying about, but differentiating the benign sounds from the unusual, potentially wear-related noises is important. With time, your hydraulic pump operators will become familiar with how the equipment sounds and which of those sounds are concerning.

Here are the most common causes of troublesome noises and what can be done:

• Aeration – Aeration typically presents with a knocking or banging sound – the result of air rapidly compressing or decompressing in various parts of the hydraulic pump. Sometimes, aeration may produce a whining sound, but it will likely be intermittent and not localized to a particular part of the hydraulic pump or system.

  Aeration is caused by air contaminating the system’s hydraulic fluid. As this air escapes into deeper parts of the hydraulic pump, it can adversely affect hydraulic fluid flow or viscosity, resulting in power delivery problems or accelerating wear.

  Stopping aeration means stopping air contamination. Specifically, this means maintaining adequate hydraulic fluid levels and ensuring the most vulnerable parts of the hydraulic pump are secured – the pump’s intake lines and fittings, as well as its drive shaft.

• Cavitation – Cavitation and aeration are often mistaken for each other, but they are distinct issues with distinct causes. They also produce distinct, unusual noises. Whereas aeration generates a banging or knocking sound, cavitation emits a high-pitched noise – which may develop into a rattle if not addressed.

  Aeration and cavitation may produce a similar-sounding whine, but cavitation tends to emit a consistent pitch and in the same spots in the hydraulic system or pump.

  Cavitation is the result of a starved hydraulic pump – one that isn’t receiving sufficient hydraulic fluid flow. During cavitation, vacuum “bubbles” form in the hydraulic fluid and collapse, causing vibrations and shock that may damage nearby components. Cavitation is a major cause of hydraulic pump failure but can often be avoided by correcting flow-related problems, including blockages or fluid viscosity issues. Blockages are most common around hydraulic fluid filters, kinked hydraulic lines, and valves.

• Valve settings or issues – Valves are another potential vulnerability in your hydraulic system and can cause problems that produce unusual noises. The relief valve, responsible for dumping pressure from the system, is only intended to engage periodically, and only for a brief amount of time. If the relief valve hisses continuously, this is a sign that it’s constantly bleeding pressure from the hydraulic system, which is an issue that must be corrected.

  Directional valves are responsible for changing the direction of hydraulic fluid flow and produce minimal sound when they’re operating normally – usually nothing more than a slight click as the spool shifts. However, if the valve or its chokes aren’t properly configured or maintained, the directional valve spools will slam instead, causing a loud bang and sending a wave of vibrations through the hydraulic pump and system. These can destabilize parts of the hydraulic pump and accelerate wear, so any slamming should be investigated promptly.

• Hydraulic cylinder binding – Hydraulic cylinders are the frequent sources of hydraulic system failures and can cause issues that also affect the pump.
  
  

  Hydraulic cylinder binding is one such issue and is the result of the cylinder rod contacting the interior surfaces of the cylinder barrel while stroking. This produces a scraping noise that should never be present while the cylinder is operating normally. In fact, hydraulic cylinders should be nearly silent while stroking.

  If a bent or slipping cylinder rod isn’t addressed promptly, it can accelerate hydraulic seal wear and introduce metal contaminants into the hydraulic pump.

• General mechanical wear – Hydraulic pumps and systems rely on an array of gears, bearings, seals and other mechanical components. As these parts wear with use, they may produce an unexpected combination of unusual noises, such as knocking, grinding, whining, banging and gurgling. If these noises tend to emerge from the same parts of your hydraulic system, it may be due to a particular component wearing out.