Causes of hydraulic pump failure

Causes of hydraulic pump failure

In any hydraulic system, the hydraulic pump is usually the most expensive component and if it fails the whole system can be rendered inactive. Hydraulic pumps are extremely sensitive to contaminants and have the highest reliability risk. When a hydraulic pump starts to fail, it can force contaminants and debris further down the system and if this is not intercepted by an effective filter, the debris can then cause damage to other components. With this in mind, it is worth knowing the warning signs of common hydraulic problems and the precautions or actions that should be taken to prevent the lost work time and expense resulting from pump failure. As experts in hydraulic pump repairs, we at CJ Plant reveal the common causes of hydraulic pump failure. 

In any mechanical system, components will be subject to wear and tear throughout their working life and will eventually wear out. Poor quality components will obviously have a shorter lifespan and should, therefore, be avoided, but there are a number of system failures common to all models of hydraulic pump that can easily be prevented if users are vigilant and pay attention to the operation of the system they are using. There are three common hydraulic pump failure symptoms that operators should be aware of that can be an indication of impending hydraulic pump failure:

Warning signs to look for

  • Hydraulic pump noise problems –

    If the hydraulic pump is making a whining noise or producing banging or knocking sounds, it can be assign of aeration or cavitation inside the pump. As the piston operates, pressure inside the pump drops and the resulting higher atmospheric pressure in the reservoir pushes hydraulic fluid along the inlet line into the pump. Anything that reduces this inlet flow can cause dissolved air in the oil to be drawn out forming air bubbles. When these reach an area of high pressure, the bubbles will implode under pressure and the resulting shockwaves will produce a high pitched whining sound. This can be assign of a damaged or blocked suction strainer or a plugged breather cap. High temperature in the fluid can also cause air to be released or low temperature can increase viscosity and slow fluid entering the pump so fluid temperature should be monitored closely. While not a common problem in the UK, systems operating high above sea level can also suffer from insufficient fluid entering the inlet due to atmospheric pressure being too low to push it through. Air from outside entering the system will result in aeration and will result in a knocking or rattling sound in the pump. As the pressure inside the system is lower than outside, any leaks in the suction line or the cylinder seal will cause air to enter the system. Poorly tightened connections on the suction line can also result in this problem. If this is suspected apply a layer of oil over any suspected location for a leak. If a hole appears in the oil as air is drawn in, the leak has been located. The noise will subside momentarily as this happens if aeration is the cause of the sound. If a leak is not located, check the reservoir. If the fluid level is too low, air can also been drawn in here or if the fluid entering the reservoir is dropping from a height it can cause bubbles to form as the fluid splashes which again can then enter the system. Any foaming of the fluid in the reservoir is another sign of aeration as the air exiting the system will cause foam to form.

  • Increased fluid temperature –

    Hydraulic fluid in a working system should never be above a temperature of eighty two degrees Celsius. A temperature exceeding this can be an indication of a malfunctioning heat exchanger or an overheating final drive motor. Cooler fins and the cooling fan should be cleaned and inspected for any damage, along with the fan belt, Any change in the pressure in the system from the manufactures settings will lead to an increase in temperature, along with other problems. Pressure levels should be checked in case deliberate or accidental adjustment of pressure has been carried out and relief valves checked in case they are damaged or incorrectly adjusted, as this can also lead to a change in system pressure and subsequent overheating. A lowered level of hydraulic fluid in the reservoir can also lead to overheating. if this is the case, the level of fluid should be topped up and the reservoir checked for any leaks that could be leading to this. All filters should checked for build up of debris or blockage as this can also affect pressure in the case of internal filters or cause insufficient flow of air in cooling systems. It is also worth considering the use of an offline filter

  • Slow operation of hydraulics –

    If your hydraulic system is running slower than usual, or showing increased cycle times, this is an indication of a drop in pressure within the system which can then lead to a subsequent overheating. This can be an indication of a leak in the system. If it is an external leak, it will usually be easy to locate and repair. However, if no external leak is visible it could be a sign of an internal leak in the gear pump or actuators and a hydraulic flow tester should be employed to test for this and locate the leak for repair.

While using good quality hydraulic fluid and implementing good contamination control systems can avoid many problems, sometimes the worst can still happen. If any of the above indicators are observed, they should not be ignored and the source of the problem located and repaired before they cause further damage. The implosion of air bubbles during cavitation can cause internal wear on the pump and dislodge debris or metallic fragments that can travel through the system, causing wear and erosion to components. These can then lead to further system failure. Aeration can lead to lowered lubrication inside the pump, leading to friction between metal components and the pump seizing up. This can not only damage the pump but also alter the pressure in the system, causing overheating and damage to other components.  Overheating can lower the viscosity of hydraulic fluid, lowering its ability to lubricate and degrading it and shortening its lifespan and causing heat damage to seals, leading to leaks.

Any one of these issues can lead to a cascade effect, causing damage to multiple parts of the overall system and resulting in lost work hours and revenue and expensive repairs. If your equipment is displaying any of these symptoms, call CJ Plant maintenance today. We understand that when your equipment is malfunctioning or damaged you need fast and efficient diagnosis and thorough professional repairs as soon as possible. We carry out hydraulic pump repair and plant maintenance to customers throughout the UK and offer free collection, wherever you are located if we cannot perform repairs on site. We will thoroughly inspect your faulty equipment and offer a full evaluation and no obligation quote for repair. After repair we will return your equipment fully restored to OEM standards with a written twelve month warranty. For further information on the services we provide, please contact us, we will be happy to help.


Telephone: 01527 535 368

Tracey Jones

Tracey Jones is the sales & marketing director at CJ Plant Maintenance and has tonnes of experience within this sector. Tracey contributes to the blog, sharing her knowledge and passion for hydraulic repair and plant maintenance.