How to Maintain a Hydraulic Pump: Warning Signs of Failure and Service Life Explained

How to Maintain a Hydraulic Pump: Warning Signs of Failure and Service Life Explained

When construction and industrial machinery is in daily operation, hydraulic system trouble and unexpected shutdowns are a common challenge.
To keep equipment running reliably and avoid unnecessary repair costs, regular inspection and prompt action are essential.

This article explains the warning signs that indicate when a hydraulic pump needs attention, practical inspection methods to help extend its life, and the proper procedure for bleeding air from the system.
It also covers the advantages of using genuine parts when repairs are needed.
Use it as a practical reference for your day-to-day operations.

Warning Signs That a Hydraulic Pump Needs Maintenance

When operating machinery on site, you may occasionally notice movement or responses that feel different from normal.
These subtle changes can be signs that it is time to inspect the hydraulic pump.

To help you address problems before the damage spreads, let’s look at three specific symptoms.

• Pressure fails to build
• Unusual noise or vibration occurs
• Hydraulic fluid leaks or turns cloudy

Do not overlook these warning signs, and check the situation promptly.

Pressure Fails to Build

If the machine feels weak or its movements become sluggish, the hydraulic pump may not be building enough pressure.
The main causes of low pressure are worn internal components, insufficient hydraulic fluid, and clogged filters.

When there is a problem somewhere along the path that transmits hydraulic pressure, the machine cannot deliver its intended performance.
Start by checking whether the hydraulic fluid level is within the proper range and whether there are any leaks from the piping.
If the filter is dirty, it will restrict fluid flow, so regular cleaning or replacement is essential.
Dealing with the problem early can reduce strain on the entire system and help keep repair costs down.

Unusual Noise or Vibration Occurs

If you hear a rattling metallic noise or feel stronger-than-usual vibration while the pump is running, it needs immediate inspection.
These abnormal sounds and vibrations may indicate damage to the internal bearings or cavitation caused by inadequate suction.
Cavitation occurs when hydraulic fluid cannot be drawn in smoothly, often because of a clogged filter, and if left unaddressed it can severely damage internal components.

As soon as you notice unusual noise, stop the machine and check the hydraulic fluid level and the condition of the filter.
Detecting the problem early can help prevent catastrophic damage to the pump itself.

Hydraulic Fluid Leaks or Turns Cloudy

If hydraulic fluid is seeping from joints or piping around the pump, the packings or seals may have deteriorated.
If the leak is left unaddressed, not only will the fluid level drop, but dirt and moisture may also enter through the gaps.

If the hydraulic fluid in the tank has turned cloudy or milky, it is a sign that water or air has entered the system.
If air is the cause, the fluid may return to clear after some time; if water has entered, it will remain cloudy.
Because water contamination can cause internal rust and severe lubrication failure, the fluid should be drained completely, the tank cleaned, and replaced with new hydraulic fluid as soon as possible.

The Typical Service Life of a Hydraulic Pump

The service life of a hydraulic pump depends on the operating environment and how frequently it is inspected.
With regular maintenance, it can generally operate reliably for around 7,000 to 9,000 hours.
If hydraulic fluid temperature is not managed properly or filters are not cleaned, performance may deteriorate within just a few years.
Regular maintenance and reducing the load on the unit are the keys to extending its service life.

Maintenance Practices That Help Extend Hydraulic Pump Life

Even small maintenance efforts in day-to-day operations can reduce equipment trouble.
To prevent unexpected failures and keep the machine operating safely over the long term, a combination of routine checks and periodic maintenance is highly effective.

The following four maintenance practices are especially important.

• Inspect the pump for hydraulic fluid leaks, unusual noise, and vibration
• Understand how contaminated hydraulic fluid affects the inside of the pump
• Measure discharge pressure and bearing temperature regularly
• Inspect seals for deterioration and determine the right time for replacement

Let’s look at each of them in turn.

Inspect the Pump for Hydraulic Fluid Leaks, Unusual Noise, and Vibration

One of the basics of daily inspection is to check the machine visually and by listening before starting operation.
Inspect the outside of the pump and the pipe connections every day for any sign of fluid seepage.
Even a small leak can eventually lead to a serious drop in hydraulic pressure.

It is also important to listen for unusual sounds and check for unnatural vibration immediately after startup or when the pump is under load.
Abnormal noise can provide an early warning of internal wear or air entering the system.
By staying alert to day-to-day changes, you can take action before the problem grows into a major repair.

Understand How Contaminated Hydraulic Fluid Affects the Inside of the Pump

Hydraulic fluid is often described as the lifeblood of the machine, and its condition has a direct impact on system life.
If metal particles, dust, or other contaminants mix into the fluid, they can wear down the pump’s precision internal components and gradually increase clearances.
As pressure escapes through those gaps, the machine may eventually stop operating properly.

To prevent contamination, check the color and viscosity of the fluid regularly and replace it completely once the specified service interval has been reached.
To ensure the filter can do its job properly, clean or replace it based on the recommended operating hours so the inside of the system stays clean.

Measure Discharge Pressure and Bearing Temperature Regularly

Objective measurements are an effective way to detect internal deterioration that cannot be identified by appearance or sound alone.
Use a pressure gauge to measure discharge pressure regularly and keep a record of whether it remains within specification.
If the pressure is gradually dropping, it may indicate that internal wear is progressing in areas that cannot be seen.

Do not forget to measure the temperature around the pump bearings as well.
If the temperature rises above the normal range, lubrication may no longer be working properly and friction may be increasing.
Keeping regular records makes it possible to schedule maintenance before components reach the end of their service life.

Inspect Seals for Deterioration and Determine the Right Time for Replacement

The seals and packings that keep the inside of the pump sealed and control fluid flow are made of rubber or resin and will deteriorate over time.
Because they are constantly exposed to heat and pressure, they gradually lose elasticity, harden, and eventually crack, causing hydraulic fluid leaks.
These parts are difficult to inspect from the outside, so their condition should be checked carefully during teardown inspections.

Rather than waiting until leakage occurs and then rushing to replace them, it is safer to replace them early based on the service hours recommended by the manufacturer.
Doing so helps reduce the risk of secondary failures.

Air-Bleeding Procedures to Prevent Air Entrapment in a Hydraulic Pump

Air entrainment in hydraulic fluid can significantly reduce machine performance.
If you know how to deal with it properly, you can resolve problems quickly during operation and restore the machine’s original performance.

Here, we will look at the issue from the following three perspectives.

• Understand what causes air to enter the system and the risks of leaving it unaddressed
• Use the air bleed valve to release trapped air
• Bleed air by operating the cylinders on the machine

Make sure you understand how each method works and follow the correct procedure to work safely.

Understand What Causes Air to Enter the System and the Risks of Leaving It Unaddressed

Air usually enters the hydraulic circuit right after hydraulic fluid has been changed or when a loose pipe connection creates a gap.
It can also be drawn in when the fluid level in the tank becomes too low.
If the system is used with air still mixed in, machine response may become sluggish and the equipment may move unpredictably, creating a safety risk.

In addition, when air bubbles collapse inside the pump, they create powerful shock waves that can erode metal components.
If you notice unusual noise or sluggish movement, stop work immediately, find the cause, and bleed the air from the system.

Use the Air Bleed Valve to Release Trapped Air

If the pump or cylinder is equipped with a dedicated air bleed valve, you can safely remove trapped air by following the correct procedure.
First, lower the system pressure to a safe level before starting the work.

Next, loosen the air bleed valve slightly and check that air is escaping together with the hydraulic fluid.
Once all the air has been released and only clear hydraulic fluid is flowing out steadily, tighten the valve again.
Do not open the valve too quickly, as hot hydraulic fluid may spray out. Turn it slowly and proceed with caution.

Bleed Air by Operating the Cylinders on the Machine

On construction equipment such as hydraulic excavators, a common way to remove air is to use the machine’s actual movements to return it to the tank through the circuit.

With the engine running at low speed, slowly move the boom, arm, bucket, and other sections.
The key is to move each component through its full range of motion several times without stopping halfway.
By repeating this process, the air trapped in the piping will be pushed out naturally.

Do not try to loosen pipe fittings to bleed air by force, as hydraulic fluid may spray out and cause burns.
Use the machine’s normal movements instead, as this is the safer method.

The Importance of Genuine Parts in Repair and Replacement

When equipment performance declines and parts need to be replaced, it can be tempting to choose low-cost third-party, counterfeit, or imitation parts.
However, from a long-term perspective, genuine parts supplied by the manufacturer are the better choice.

Here, we will focus on the following two points.

• The risks associated with non-genuine or low-cost alternative parts
• Reliable identification and ordering of genuine parts using apps and other tools

Understanding how differences in quality can affect future performance will help you choose the right parts.

The Risks Associated with Non-Genuine or Low-Cost Alternative Parts

The market is full of inexpensive parts that closely resemble genuine manufacturer products but are not official parts.
These alternatives often lack dimensional precision or sufficient material strength.
Even a slight dimensional discrepancy can cause hydraulic fluid leaks, and insufficient strength may lead to another failure in a short period of time.

In addition, if using non-genuine parts causes damage to other areas, the manufacturer’s warranty may no longer apply.
Be careful not to focus only on short-term savings and end up facing much larger repair costs later.

Reliable Identification and Ordering of Genuine Parts Using Apps and Other Tools

To obtain the correct genuine parts, it is essential to know the model number and part number of the equipment currently in use.
Today, convenient apps and services are available that let you identify genuine parts quickly using a smartphone.
These tools save you the trouble of searching through complex catalogs and help prevent mistakes when ordering parts.

By entering the serial number on the nameplate, you can identify compatible parts, and if the number is hard to read, you can sometimes send a photo and receive support.
To shorten repair time and streamline maintenance work, make active use of these modern tools.

Summary: Extend Machine Life Through Proper Hydraulic Pump Maintenance

Using genuine parts is essential for maintaining the high performance of construction machinery and preventing downtime.
At the same time, the market today is full of low-quality non-genuine parts that can lead to poor performance and premature failure.
When arranging replacement parts, working through an authorized dealer is the most reliable approach.

When it is time to replace parts, make use of Kawasaki Hydraulic Finder, which is available on smartphones and the web.
By using the serial number shown on the unit’s nameplate, you can identify genuine parts, obtain accurate information, and contact an authorized dealer.
Secure the right parts and keep your machinery operating longer.

Reviewed by

Ryoji Irie

Manager
After-Sales Promotion Office, Marketing & Sales Group, Precision Machinery & Robot Company, Kawasaki Heavy Industries, Ltd.

《Career History》

After joining Kawasaki Heavy Industries, I spent ten years developing the new K7V pump series as a design engineer, followed by five years at KPM (UK) as an application engineer supporting European OEMs and distributors. I am currently responsible for promoting the after-sales business globally.