most common causes of hydraulic systems failure

Most Common Causes of Hydraulic Systems Failure

Author: Michele Baker Ph.D

When a hydraulic system fails, finding the source of the problem can be a challenge. Though hydraulic systems primarily consist of a sump, motor, pump, valves, actuators and hydraulic fluid, any of these parts could be the source of failure. That's not to mention the additional potential for failure through human error and faulty maintenance practices. If your system fails, you need to know why it fails, how to find the failure and how to keep it running smoothly in the future, all while keeping personnel safe.

Table of Contents

  1. Common Causes of Hydraulic Failure
  2. Hydraulic System Troubleshooting
  3. How to Solve Common Hydraulic Problems
  4. How to Prevent Hydraulic System Failure
  5. Hydraulic System Maintenance
  6. How to Work Safely With Hydraulics

Common Causes of Hydraulic Failure

It's often easy to tell when a hydraulic system fails — symptoms can include high temperatures, low pressure readings and slow or erratic operation are glaring problems. But what are the most common causes of hydraulic systems failures? We can trace most hydraulic issues back to a few common causes, listed below.

1. Air and Water Contamination

air water contamination

Air and water contamination are the leading causes of hydraulic failure, accounting for 80 to 90% of hydraulic failures. Faulty pumps, system breaches or temperature issues often cause both types of contamination.

Air contamination is the entrance of air into a hydraulic system and consists of two types — aeration and cavitation. Both can cause severe damage to the hydraulic system over time by wearing down the pump and surrounding components, contaminating hydraulic fluids and even overheating the system. Although we are not pump manufacturers, we know it is essential to be aware of these types of contamination and how to identify their symptoms.


  • Cavitation: Hydraulic oil consists of about 9% dissolved air, which the pump can pull out and implode, causing pump problems and damage to the pump and to other components in a hydraulic system over time. You can identify this problem if your hydraulic pump is making a whining noise.
  • Aeration: Aeration occurs when air enters the pump cavity from an outside source. Usually, loose connections or leaks in the system cause this issue. Aeration also creates a sound when the pump is running, which sounds like knocking.



Water contamination is also a common problem in hydraulic systems, often caused by system leaks or condensation due to temperature changes. Water can degrade hydraulic components over time through oxidation and freeze damage. A milky appearance in hydraulic fluid can help you identify water contamination.

2. Temperature Problems

Hydraulic systems that run too hot or too cold can cause severe problems over time. Some of these challenges include the following symptoms.


  • Fluid thinning: Heat can cause hydraulic fluids to thin, preventing lubrication and making the fluid more likely to leak.
  • Fluid oxidization: Extreme heat can cause hydraulic fluid to oxidize and thicken. This fluid thickening can cause buildups in the system that restrict flow, but can also further reduce the ability of the system to dissipate heat.
  • Fluid thickening: Low temperatures increase the viscosity of hydraulic oil, making it harder for the oil to reach the pump. Putting systems under load before the oil reaches 70 degrees or more can damage the system through cavitation.


Poor heat dissipation is the usual suspect behind heat buildup, while environmental factors most often cause too-cool systems.

3. Fluid Levels and Quality

Fluid levels and quality can affect hydraulic system performance. Low fluid levels and inappropriate filtration can result in air contamination, while fluid contamination can cause temperature problems. Leaks can further exacerbate both issues.

Using the correct type of fluid is also essential, as certain hydraulic oils are compatible with specific applications. There are even oil options that offer higher resistance to temperature-related problems. Some oils even offer anti-wear and anti-foam additives to help prevent against wear and air contamination, respectively.

4. Human Error

human error is the base cause of many hydraulic system problems

Human error is the base cause of many hydraulic system problems. Some of the most common errors that may result in your hydraulic pump not building pressure include the following.


  • Faulty installations: Improper installation of any component in a hydraulic system can result in severe errors. For example, the pump shaft may be rotating in the wrong direction, negatively affecting pressure buildup, or pipes may be incorrectly fitted, resulting in leaks.
  • Incompatible parts: An inexperienced installer may put mismatched components together, resulting in functional failures. For example, a pump may have a motor that runs beyond its maximum drive speed.
  • Improper maintenance or usage: Using systems outside their operational capabilities or failing to perform regular maintenance are some of the most common causes of hydraulic system damage, but are easy to rectify through updated maintenance policies and training.


Hydraulic System Troubleshooting

The sources of system failures can be tricky to identify, but some hydraulic troubleshooting steps can help narrow down the options. So how do you troubleshoot a hydraulic system? Here are some of the fundamentals.

  • Check the motor: Ensure the motor has the correct wiring and can turn on and off.
  • Check the pump: Take the pump assembly apart and assess all parts to ensure that they are functional and installed correctly. The most common problem areas include the pump shaft, coupling and filter.
  • Check the fluids: Check the level, color and viscosity of the hydraulic oil to ensure it meets specifications and has not become contaminated. Low hydraulic fluid symptoms include pressure or power loss. When in doubt, drain and replace the fluids.
  • Check the seals: Look for evidence of any fluid leakage around your hydraulic system's seals, especially the shaft seal. Leakage can indicate worn-out or blown seals that can cause malfunctions with pumps, motors and control valves.
  • Check the filters: Ensure filters are clear of plugs and blockages. Common clogged hydraulic filter symptoms include sluggish operation and noisy operation.
  • Check valves and lines: Observe all lines for potential leaks, and tighten every connection point. Also, check the relief valve for any signs of damage.
  • Run the system: When you have completed all these essential checks, turn on the system and monitor it for pressure and temperature fluctuations, as well as abnormal sounds. If all seems well, check your pressure sensor for potential failure.


How to Solve Common Hydraulic Problems

So if your system is not functioning properly, how do you solve hydraulic problems? Start your diagnosis with the symptoms you notice.

1. The System Does Not Operate, Runs Too Slowly or Quickly, or Performs Unpredictably.

Common fixes for these issues include:

  • Use the specified fluid amounts, types and viscosity by reviewing your manual and replacing or topping off as necessary.
  • Check for oil leaks or line blockages, secure fittings, and clean or replace lines if needed.
  • Allow for recommended system warmup time to achieve proper oil viscosity and temperature.
  • Check and clean or replace clogged or dirty filters.
  • Repair or swap out leaking suction lines.
  • Verify pressure compensator settings on variable displacement pumps and pressure relief valves.
  • Clean dirty components and fix or change out any you notice with excessive wear.
  • Check pump drive belts and hardware for correct alignment and tension.
  • Verify you are operating within your equipment's load limits and manufacturer-recommended engine operating speeds.
  •  Adjust restrictors and relief valves accurately as indicated in your owner's manual.

2. The Oil Foams or Overheats.

Typical fixes for these issues include:

  • Ensure the oil is clean, full and of the recommended type.
  • Confirm you have the correct reservoir size and cleanliness, and clean or replace if needed.
  • Check the oil cooler for proper operation and fix or change it out as needed.
  • Confirm that engine speed is within suggested manufacturer limits.
  • Clean, repair or replace clogged or leaking filters and lines.
  • Place the control valve in neutral when idle.

3. The Control Valve Binds, Drops Load or Leaks.

There are ways to eliminate these issues, such as:

  • Replace worn cylinder fittings and seals.
  • Verify linkage and repair spool binding.
  • Ensure proper valve alignment and swap out worn or damaged valves.
  • Adjust the tension on tie bolts and bracket screws.
  • Replace any components with visible cracks or other damage.

4. The Cylinder Leaks, Knocks or Lowers Incorrectly.

To fix these common hydraulic problems, you want to:

  • Replace any rods and seals with noticeable damage or wear.
  • Verify your load check is functioning and install a new one if needed.
  • Check for air in your fluids and remove it or replace leaking lines.
  • Swap out packing and center the actuator.
  • Replace leaking cylinder seals.
  • Verify valve type is correct for load and use manufacturer-recommended valves.


How to Prevent Hydraulic System Failure

Hydraulic system issues are inevitable at some point. However, simple steps can help you avoid these issues and increase the longevity of your hydraulic system. On top of effective troubleshooting, you can prevent hydraulic system failure by taking the following steps.


  • Follow specifications: We can trace the most common hydraulic system issues back to fundamental system problems like incompatible or improperly installed parts. For this reason, it's essential to always double-check specifications to ensure your purchased parts can work together seamlessly.
  • Consult with professionals: When purchasing new equipment, consult with industry peers and professionals to discover what they recommend. While manufacturers can tell you how a product should work, industry professionals can provide concrete examples of how well the equipment works for their industry.
  • Perform maintenance: It is essential to focus your operations on equipment longevity. Review your daily, monthly and annual maintenance procedures to ensure you are covering every aspect of your system according to best maintenance practices and catch symptoms early on.

On top of these steps, look into hydraulic system products that are specifically designed to help prevent failures. One such product is Bear-Loc® by York Precision. This innovative locking actuator is a safe, reliable feature for hydraulic components, automatically locking when sleeve pressure is relieved, preventing movement if a hydraulic system fails. This way, your can protect your personnel from injuries related to hydraulic failures. Even better, York Precision offers in-house design, engineering expertise and machining and manufacturing capabilities to produce a hydraulic locking device that meets your exact specifications.


Hydraulic System Maintenance

Regularly review hydraulic system maintenance, always following manufacturer recommendations and industry best practices. Also, consider the storage condition, external influences, working pressure and usage frequency of your system to tailor your maintenance schedule and procedures.

Generally speaking, you should perform maintenance at three levels.


  • Daily tasks: Take care of a few simple daily checks to avoid issues. For example, personnel should check the oil levels, hoses and connections and listen to the pump for abnormal sounds.
  • Routine tasks: Plan and execute a weekly and monthly maintenance routine, checking for the most common failure sources given your system's working conditions. These should include components, filters and the condition of the oil.
  • Complete system checks: Depending on the conditions of your system, you and your team should perform complete systems checks monthly, quarterly or annually. Tasks should include running a comprehensive report on the system, cleaning devices, draining the system and replacing damaged parts.


How to Work Safely With Hydraulics

how to work safely with hydraulics

When completing system maintenance, it is essential to follow basic safety procedures. Faulty or broken parts can cause leaks, bursts and projectiles that can severely injure personnel. Some common injuries include bruises, cuts and abrasions. However, pinhole leaks can inject oil into the body, causing septicemia that can result in the loss of a limb if not addressed immediately. To avoid these injuries, be sure to follow basic safety guidelines.


  • Wear safety equipment: Always wear appropriate safety gear when working close to a system, including a helmet, glasses, gloves and protective clothing and shoes.
  • Power down systems: Never service a running hydraulic system unless it is strictly necessary.
  • Be mindful of location: Do not stand at endpoints while working on hydraulic systems. This safety measure can help prevent loss of limb and life, as there is a lot of pressure built up in these areas that can release and result in life-threatening situations.
  • Use safety locks: Hydraulic safety locks save lives. Always use these when transporting or lifting equipment for service.
  • Use caution around running systems: Always keep an eye out on pressure taps, couplings and hoses when they are under pressure. If something does not look right, power down the system before checking it. Loose or faulty parts can easily become deadly projectiles.

The best safety measures, however, are to perform excellent maintenance and use high-quality parts. If you're looking for a quality hydraulic component manufacturer, York Precision Machining & Hydraulics can help.

Choose York PMH for Hydraulics Help

At York Precision Machining & Hydraulics, we highly value safety and know many of our clients are interested in the topic of hydraulic systems failure. People want to know how hydraulic systems fail, which is why we wanted to share this information with you. If you're interested in learning more about fluid power components and systems, you can trust us to help.

York Precision Machining & Hydraulics is an industry leader in precision fluid power components and systems. We are a top components manufacturer for aerospace, defense, commercial and industrial businesses worldwide, operating out of a state-of-the-art 65,000-square-foot facility in York, PA. With nearly 50 years of industry experience, we set the standard for hydraulic fluid power components. If you need hydraulic equipment, York PMH is fully equipped to handle your project from design to assembly.

Contact York Precision Machining & Hydraulics today for all your hydraulic needs.

York Precisions Is Your Fluid Power Actuator Experts

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