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Hydraulic Pump Cavitation: Causes & Symptoms

Cavitation is the second leading hydraulic pump failure cause, behind contamination. As this can potentially cause damage and compromise your hydraulic system, it is important to understand what it is as well as its symptoms.

What is Cavitation?

Cavitation is the product of excessive vacuum conditions created at the hydraulic pump’s inlet. This causes high vacuums to create vapour bubbles within the hydraulic oil, these are then carried to the discharge side before they then collapse - causing cavitation to occur.

These high vacuums and cavitation are often caused by poor plumbing, flow restrictions, or high oil viscosity. Poor plumbing is often the main cause of this and is due to an incorrectly sized hose or fittings and/or an indirect (not straight or vertical) path from the pump to the reservoir.

Unfortunately cavitation is not where the problem ends. Cavitation causes:

  • Excessive heat,
  • Violent implosions - when the bubble dispurses, this draws materials into the space where the bubble was.
  • Reduced lubrication - as there is air being pulled through the fluid there is less fluid to provide lubrication within the system.
  • Friction and wear - due to the reduced level of fluid within the pump the protective layer is reduced causing materials to rub on other components.

All of these can cause the hydraulic pump to fail and damage the components within it.

What are the Symptoms of Cavitation?


The easiest way to identify cavitation is through noise. The hydraulic pump will either emit a “whining” or a “rattling” sound. If you hear either or both of these sounds you will need to isolate the pump to make sure that this is where it is coming from.

The Presence of Metallic Debris in the Filter

As part of your general maintenance, you should be inspecting and replacing the hydraulic oil filter's elements at regular intervals based on the duty cycle of the application and how often it is used. If when replacing the filter you come to find metallic debris this could be a sign that cavitation is occurring within the pump. In this case it is best to flush the entire system and detach the pump for closer inspection.


When replacing the filter you find that it is damaged, this could be due to cavitation. To find out if this is the case, remove the filter element of the hydraulic system and inspect for metallic debris. If there is some present then flush the system to prevent damage being caused elsewhere. Now that you have identified cavitation has been occurring within the hydraulic pump, you’ll need to determine the exact cause of cavitation.

As there are so many causes and damage results from cavitation, it is important to regularly check your hydraulic pump for signs of cavitation. By simply checking the pump and filter you can prevent your hydraulic system from failing when you most need it.

Hydraulic pumps come in a variety of sizes, styles and fuel types, so if you are having issues with your pump browse our great range for a replacement or get in contact with our expert team for advice on any hydraulic issue.

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