What Causes Hydraulic Pump Failure?

A hydraulic pump is an essential component of any excavator. The hydraulic pump is a mechanical part of an excavator. It converts the hydraulic energy into mechanical force to perform various operations on the job site.

The excavator’s hydraulic system controls the speed and direction of movement, thus controlling the digging machine’s operation.

When it faces failure, it means you will bear the downtime and extra expenses. If you can detect what causes the failure, you can prevent this from happening.

This article will help you get familiar with major pump failure signs. You will also know about the causes of pump failure. Sounds good? Let’s begin!

Major Signs of Hydraulic Pump Failure

Several signs can point out there is something wrong with your hydraulic pump. Some of the major signs are as follows:

1.    Knocking

Generally, knocking is an audible noise that the parts of a hydraulic pump produce. Knocking results when air gets mixed in your hydraulic fluid. It occurs when the fluid is compressed or decompresses in the fluid. It tries to escape the fluid making a banging noise.

It can be a sign of failure for your hydraulic pump. Especially when there is high demand at the same time and vibrations are very strong. Incorrect oiling results in a knocking noise. It also occurs when you store your oil in the air, or a leaking seal may also contribute to knocking. As it allows the mixing of air in the hydraulic fluid.

2.    Sudden Decrease in Pressure

A sudden decrease in pressure is a condition where the normal pressure of the hydraulic system drops below its minimum operating pressure. It occurs when the pump has low oil levels, especially in the suction port.

It leads to higher vacuum pressure. This dissolved air removes the oil on the suction part and collapses on the pressure part. This is how a sudden decrease in pressure occurs.

3.    Faulty Final Drive Hydraulic Motor

A major sign indicating that your hydraulic pump will fail soon is a weak or faulty final drive motor. It arises from many causes, such as partial failure of the pump, manufacturing defects, and worn components.

The severe contamination also leads to this issue. The weak final drive motor is unable to build up necessary pressure. This is why it also leads to a weak hydraulic system.

4.    Hydraulic Fluid Leakage

Hydraulic leakage refers to the leaking hydraulic fluid out of your hydraulic system. Hydraulic fluid leaks can occur for several reasons, such as a broken seal, gasket, or case. When a hydraulic fluid leakage happens.

It will act as a sign of hydraulic pump failure and need repair right away. Leakage results in less or no oil in your hydraulic pump. This eventually leads to severe wear and tear when the metal comes into contact without oil.

5.    Periodic Failure of Pump Seals

Periodic Pump seal failure is a common problem with all types of pumps. It is caused when the pump seal often becomes dry and cracks. It can be due to the following reasons: –

  • Seals wear out due to constant rubbing against abraded surfaces.
  • The hydraulic fluid often contains abrasive particles, which may cause seals to wear out over time.
  • Stress buildup and fatigue because of pressure on the seal area during operation.
  • Use of inferior materials rather than metal inserts

Timely oil replacement, periodic lubrication, and correct installation of seals may prevent seal failure.

6.    Weak/ Faulty Cylinder Operation

Weak cylinder operation is the hydraulic pump’s inability to produce sufficient output pressure. Various failure scenarios can cause weak cylinder operation

  • Internal contamination
  • Water in oil
  • Metal particles blocking the oil passages

Weak cylinder operation mainly leads to the ineffective functioning of various hydraulic components. These components include boom cylinder, arm cylinder, stick cylinder, final drive motor, bucket cylinder, etc.

7.    High Temperature During Cylinder Operation

High temperature refers to the hydraulic fluid’s heat from continuous working. It may be due to the cooling system not working appropriately. The hot oil can damage seals making the pump non-operational. Typically, high temperature during cylinder operation indicates a breakdown in the hydraulic pump.

The hydraulic pump will cease to function due to the excessive wear and tear on components. Especially those components that cannot operate under high temperatures.

The high temperature alters the composition of the hydraulic fluid, breakdown its molecules, and transforms working viscosities. Therefore, you must avoid rising temperatures beyond a specific limit.

If you detect any sign mentioned above, please note it does not reflect the pump failure. Instead, it reflects that something wrong is about to happen with your hydraulic pump.

What Causes Pump Failure?

Several issues may lead to your hydraulic pump failure. Mentioned below are some of the key issues. These issues include air contamination, normal wear and tear, general contamination, and bent rod. Now we will discuss each issue one by one.

1.    Air Contamination

Suppose the air gets mixed in your hydraulic fluid within the hydraulic pump. You will start noticing vibrations or banging noise. With time, these sounds worsen, and the heat builds up in your pump.

This may eventually lead to severe damage to the internal components of your hydraulic pump. The performance and effectiveness of your pump diminish shortly, resulting in a badly damaged hydraulic pump. The main air source inside your hydraulic pump is leaking seals or joints.

2.    Misaligned or Bent Rod

A bent rod refers to the mechanical misalignment. It is a situation where the rod can no longer align in the correct position.

A misaligned or bent rod results in the misaligned swash plate to its working angle. It is difficult to obtain the proper plunger force to achieve the desired feed rate. This can lead to a clogged pump line, causing it to fail.

Another consequence you will experience with the misaligned or bent rod is periodic seal failure. It would be best if you replaced the faulty seals more often. When a seal leaks, it may lead to severe contamination.

3.    General Contamination

Contamination is a sudden chemical or physical change. It occurs when water, dirt, and the chemicals used in the hydraulic fluid are allowed to seep into it.

Contamination is the leading cause of the failure of the hydraulic pump. It is even getting worse when you don’t notice the level of contamination within your hydraulic pump.

Protecting your hydraulic pump from such contamination levels saves hundreds or even thousands. In other words, you will spend on replacing or repairing your hydraulic pump.

4.    Common Wear and Tear

It is sad to say that no pump exists in the industry that lasts forever. Wear and Tear are a natural part of mechanical components.

The wearing to failure happens when the material breaks down over time through normal operation and improper maintenance. Some components need replacement more often within your hydraulic pump.

These components include seals or bearings. If you ignore the timely replacement of these components, it may result in catastrophic failure of your pump.

In case you come to know that your hydraulic pump needs tuning or repair. It would help if you did it on time. This will result in pump life extension and contribute to the boost in overall machine productivity.


A hydraulic pump is a vital component of your vehicle. It makes most of the components work effectively on site. When a hydraulic pump faces failure, the expenditures associated with your pump boost to an unbearable limit. This is the main reason that you should not ignore the major signs of pump failure:

  • Banging or Knocking noise
  • Pressure Drop
  • Weak or Faulty Final Drive
  • Seals Leakage
  • Weak Cylinder Working
  • Higher Temperature

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Contact us today at Xugong – excavator hydraulic pump repair specialists, to have your excavators in top shape in no time!


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