Hydraulic System Problems and Solutions: Practical Troubleshooting Guide

Hydraulic systems will experience a variety of problems at different levels during operation. Some problems involve only a single component and can be solved by replacing it. Others require optimization or even redesign at the system level. This article will list common hydraulic system problems and teach you how to solve them.

How to Quickly Assess the Severity of Hydraulic System Problems？

The core of determining the severity of a hydraulic system failure is to judge whether there is a risk of loss of control or irreversible damage to the system. I’ve listed some common phenomena and divided them into three categories to help you quickly determine the severity of the problem.

When these problems occur in the hydraulic system, it means you need to shut down immediately.

• The oil temperature exceeds the design value, the temperature rises rapidly, and cannot be stabilized.
• The pressure gauge needle is shaking, and the pressure is suddenly high and low under the same working conditions.
• Pump noise becomes louder, and speed decreases.

When these problems occur in a hydraulic system, it means that the system can still operate in the short term, but it is wearing out rapidly.

• The fluid becomes darker in color, has visible bubbles or emulsification, and has a burning odor.
• The system slows down under the same load, energy consumption rises, and heat generation increases.

When these problems occur in the hydraulic system, it means that the problem is not very serious, and you can keep watching for a while.

• The system leaks oil slightly, but it does not affect the pressure and performance.
• The system has a short noise during the cold start phase.
• The system fluctuates slightly only under extreme operating conditions.

Common Hydraulic System Problems

In this section, I will explain the possible problems behind the phenomena that can often be observed during the operation of a hydraulic system.

Excessive Noise and Vibration

There are several main types of noise and vibration, each corresponding to a different problem.

High-Frequency Continuous Noise

This sound is sharper and lasts longer. It tends to occur when there is a change in system load. It mostly appears near the pump or suction line.

If this condition weakens significantly as the oil temperature rises, it means that the problem is probably related to a clogged filter, a small pipe diameter, or an improperly selected viscosity of the oil. If it continues after the oil temperature rises, there may be a problem with the suction design.

Intermittent Knocking or Impact Noise

This irregular knocking sound is usually accompanied by a large vibration and is more obvious when the load changes.

This sound is usually caused by air leakage on the suction side or unstable oil supply. When this sound occurs, the problem is more serious. If the operation continues, it can easily lead to irreversible damage to the pump.

Low-Frequency Humming or System Resonance

This sound is not sharp, but it is continuous and more oppressive. It is most noticeable under certain operating conditions or speed intervals, and at the same time, there is a large vibration in the pipeline or the entire machine.

This sound is mainly due to a mismatch between the characteristics of the hydraulic system itself and the actual working conditions, resulting in pressure fluctuations in the system. When the frequency of these fluctuations happens to be close to the vibration frequency of the pipeline, it will trigger resonance. If the support structure is not strong enough, the vibration and noise will become larger.

Soft, Irregular Noise with Unstable Motion

When this sound occurs, you will usually notice unstable action of the actuator, and you can also see bubbles coming out of the oil tank.

This is usually due to poorly designed oil suction or return, resulting in low oil levels or leaks at sealing points. If this condition persists for a long period of time, it can reduce system efficiency and accelerate wear.

Noise Increasing Over Time with Rising Temperature

This noise will gradually become louder, while the oil temperature will gradually increase, and the efficiency of the system will decrease.

Once this noise occurs, it is a sign that the internal leaks in the system are getting progressively worse and the cavitation/aeration is long-lasting. This is not caused by one problem, but by multiple problems combined.

The table below will help you visually determine the type of noise and possible causes.

Hydraulic System Overheating

Continuous High Temperature

If the oil temperature remains above the design range for a long time, and the cooler continues to operate but is not effective, it may be because the system has serious internal leakage, or the hydraulic valve has been throttled for a long time. Finally, the energy input into the hydraulic system is not converted into mechanical output, but into thermal energy.

Intermittent Temperature Rise

If the oil temperature is normal at no load or light load, and the oil temperature only rises under specific actions, speeds, or loads, it means that the cooling capacity of the cooler is insufficient when the hydraulic system is faced with a sudden increase in load, or when certain actions are performed. The rate of heat generation exceeds the ability of the system to dissipate heat.

Slow or Unstable Actuator Movement

Consistently Slow Movement

If the actuator is moving only slowly, without jerks and crawls, and this is true regardless of load changes, there is insufficient flow in the hydraulic system. This may be caused by a hydraulic valve opening that is too small, or by insufficient displacement or speed of the hydraulic pump.

Unstable or Fluctuating Movement

If the actuator moves quickly or slowly, and is accompanied by noise or pressure fluctuations, it means that the pressure and flow rate of the hydraulic system cannot be transmitted smoothly, and energy is built up before it is suddenly released. This may be caused by an internal leak in the hydraulic system or by air being mixed into the system.

Jerky or Creeping Movement

If the actuator movement at low speeds is stop-and-go and cannot be accurately positioned, the actuator does not have enough driving force to counteract the friction between the piston and the cylinder wall. This may be due to an internal leak in the system or a lack of control accuracy.

Pressure Loss or Fluctuation

Static Pressure Loss

If the actuator does not respond when it is supposed to act, and the pressure gauge shows that the pressure has not reached the set value and is gradually decreasing, it means that the hydraulic system is unable to build up and maintain sufficient pressure, and the energy is released directly within the system. This is probably due to leaks within the system or in the piping joints.

Dynamic Pressure Fluctuation

If the action of the actuator is not smooth, the pressure is always high and low, accompanied by noise and vibration. It means that when the load or speed changes, the hydraulic system can not adjust the pressure in time. This is probably because the hydraulic pump can not provide continuous flow, the response speed of the control valve is delayed, or the characteristics of the hydraulic system and the actual working conditions do not match.

External and Internal Leakage

External Leakage

An external leak is when oil flows out of the system boundary, and you can see traces of oil on the floor or equipment surface. It is mainly caused by deteriorating seals and joints in the piping. This kind of problem is not very serious and can be easily detected, but it still needs to be dealt with in time if your working environment has safety or environmental requirements.

Internal Leakage

Internal leakage means that the hydraulic oil does not push the actuator element, but flows directly back into the tank from the hydraulic valve or a gap in the hydraulic cylinder. This situation is more invisible and will generally be reflected in a gradual increase in oil temperature, and the actuator action slows down. It will force the pump and valve to work on overload for a long time, accelerating the aging of the oil and seals.

Root Cause Analysis: Component Failure or System Design Issue?

When is a Component Replacement Enough？

When a problem with a hydraulic system is centered on a single circuit and the rest of the system is working fine, you can fix it by replacing parts. The following are common for this type of problem.

Actuator Does Not Move or Moves Only in One Direction

If an actuator does not move at all when it is supposed to act, or only extends/retracts, and all other circuits are normal, it means that there is only a problem with this actuator, and you can fix it by replacing the directional control valve, the actuator seals, or the electrical connectors.

Sudden Pressure Loss in a Specific Circuit

If the pressure on one circuit suddenly won’t go up, but the pressure on all the other circuits is normal, it means that the pressure is released by a pressure relief valve or check valve, and you just need to replace it to build up the pressure again.

Erratic or Delayed Valve Response

If you notice that a particular hydraulic valve is responding slowly, with normal control signals but inconsistent action, it means that there is wear or contamination inside the hydraulic valve, and you simply need to replace it with a new one.

Persistent External Oil Leakage at One Location

If there is a leak somewhere on the surface of the hydraulic system and there is no noticeable change in the performance of the system, it means that the seals in this area have failed, and you can fix it by replacing the seals or fittings.

Incorrect or Unstable Pressure Readings

If the display value of the pressure is abnormal, or if the actual action doesn’t match the reading, but the system still operates normally, it means that the pressure measurement is not accurate enough, and you can fix it by simply replacing the pressure gauge or pressure sensor.

Localized Overheating Near One Component

If a component is getting hot, but the overall temperature of the hydraulic system is not rising, it means there is just a throttling or leak somewhere, and you can fix it by replacing the flow control valve or throttle.

What Must Be Verified After Replacement?

After replacing the parts, you should check these points:

• Whether the action of the actuator is normal.
• Is the pressure up to standard and stable?
• Is the flow rate smooth and without abnormal fluctuation?
• The oil temperature is within the normal range.
• The oil temperature is within the normal range.
• The actuator can perform the same action multiple times.

If the answer to all of the above questions is yes, then the problem is completely solved.

When Does the Problem Indicate a System-Level Problem？

Unstable Actuator + Pressure Fluctuation

This situation is due to the fact that the reaction speed and buffering capacity of the hydraulic system cannot keep up with the actual working conditions. This fluctuation exacerbates internal leakage in pumps, valves, and actuators, converting energy into heat. At the same time, changes in pressure on the suction side also tend to bring in air. This makes the hydraulic system’s oil supply always intermittent. It also leads to unstable actuator action.

You should first improve the system circuit to make sure that the flow rate and pressure are properly distributed to solve this problem. You should then make sure that the suction and return lines are laid out correctly, and also make sure that the oil level is sufficient to maintain a stable oil supply. On this basis, you should then match the appropriate pumps and valves to reduce internal leakage and energy loss. Finally, you should remove the air from the system and eliminate the foam among the oil to prevent the air from affecting the operation of the system again.

Continuous Overheating + Pressure Instability + Noise/Vibration

This happens when there are internal leaks within the system or when air is mixed into the system. In this case, it is difficult to keep the pressure stable, and the energy cannot be continuously and smoothly transferred to the actuating elements. It can only be released repeatedly in the system. If the layout of the pipeline or support structure is unreasonable at this time, these pressure fluctuations will be expanded, causing pipeline vibration and noise. The operation of the hydraulic system will also become more and more unstable.

For this situation, you should remove the air in the system, as air can directly cause unstable pressure and abnormal noise. Based on this, you should check and optimize the piping layout, fix the pipes, and avoid excessive vibration of the pipes. After that, for possible internal leakage, you should replace the relevant parts. Finally, you should adjust the working parameters of the pumps and valves according to the actual operating conditions to make sure that the heat load of the system is within the controllable range.

Multiple Actuators Failing at The Same Time

If you design a system without considering the distribution of loads or the sequence of actions of the various actuating elements, the overall flow rate tends to be unevenly distributed, and some circuits steal too much flow during operation. The resulting pressure fluctuations can be transmitted across multiple circuits, triggering an abnormal movement of multiple actuators, giving the appearance that all actuators have failed.

For this type of problem, you should check the capacity and actual performance of the pump to confirm that it can meet the requirements of the system under maximum load. On this basis, you need to redesign or optimize the flow distribution and pressure control strategy of the circuits to avoid mutual interference between the circuits. Finally, you need to fix problems in the system and coordinate the action sequence of multiple actuators to make sure the system can operate stably under various working conditions.

Repeated Component Replacement Fails

When you have replaced valves, seals, or other components several times and still can not completely solve the problem, it usually means that the problem is not from a single component, but the structure of the hydraulic system is not reasonable. Since the basic problem of internal leakage, insufficient flow, or air mixing has not been solved, the newly replaced parts soon become abnormal again in the same situation, resulting in repeated failures.

For problems that can’t be solved by replacing parts, you should check that the layout of the pipes and the circuit design are reasonable. On this basis, you should also further optimize the control method to reduce internal conflicts in the system. At the same time, you should troubleshoot hidden internal leak points and problems in the suction circuit to avoid repeated failures.

Here’s a table to help you quickly determine which problems are with individual components and which are system problems.

Step-by-Step Hydraulic System Troubleshooting Process

Initial Visual and Operational Checks

Without stopping the machine, you can do some primary checks first to determine if there are any abnormalities in the system. You can check these contents.

• Observe the fuel level and color of the fluid in the tank, and check if the fluid is normal in color and if there are any contaminants in it.
• Check lines and fittings for obvious leaks.
• Listen to the sound of system operation and determine whether there is any abnormal noise or vibration.
• Observe whether the action of the actuating element is smooth and the speed is normal.
• Observe for significant fluctuations in pressure and flow meter readings.

These checks can be done without stopping the machine. They can provide direction for more in-depth troubleshooting.

Hydraulic Fluid and Contamination Assessment

The condition of the hydraulic fluid can indicate how healthy the system is. You can spot the following problems by watching the fluid and doing some tests on it:

• If there are too many contaminating particles, it means that there is serious internal wear and tear on the pumps or valves. This may lead to the actuating elements not working properly.
• If moisture or air is mixed into the system, it can cause pressure fluctuations and noise, and the efficiency of the system can be reduced.
• If the oil is discolored or oxidized very badly, it means that the oil temperature is too high when the system is running.

Pressure, Flow, and Temperature Verification

Pressure, flow, and oil temperature are the three core parameters of a hydraulic system, and they are interrelated. You can see how the pressure, flow, and temperature are changing together. This helps you to know if a part is failing or if the whole system is having problems.

If you look at the pressure alone, you could misjudge it as a faulty pump or valve. But if you look at it in combination with flow and temperature, you can distinguish whether it’s a problem with a single component or the whole system.

If the flow rate is too slow but the pressure is stable, this may be due to clogs or a blockage. If the flow is unstable and the pressure fluctuates, it could be caused by an internal leak in the system or an insufficient performance of the hydraulic pump.

Looking at the temperature alone, you might think that the hydraulic fluid has aged, but if it is accompanied by fluctuating pressure and erratic flow, it means that the efficiency of the system is decreasing.

Finding the Right Moment to Ask for More Help

When you’re trying to fix the hydraulic system, you need to know when to keep looking for problems locally and when to do a full check to save time and money. When the following situations occur, it is usually not a problem with individual components, but with the system design or operating conditions. At this point, you should stop troubleshooting and escalate to a systematic diagnosis or let a professional help you.

Even after the visual inspection, fluid analysis, and parameter verification are completed, the problem still recurs.

Pressure, flow, and temperature are abnormal at the same time, or actuators in multiple circuits are acting abnormally at the same time.

After multiple replacements of valves, seals, or pumps, the system continues to exhibit erratic action, noise, vibration, or heat.

Practical Solutions: Temporary Fixes vs Long-Term Improvements

When dealing with hydraulic system failures, you have to distinguish between short-term emergency measures and long-term system optimization.

Temporary Measures to Reduce Downtime

The main effect of contingency measures is to keep the system running and reduce downtime losses, but they do not solve the underlying problem. You can do these things below.

• Temporarily replacing damaged valves or seals.
• Adjusting the pump or valve pressure or flow.
• Temporarily increasing cushioning or reducing loads.
• Replacing fluids or simply venting.

These operations can only delay the deterioration of the fault, and can not guarantee the long-term stable operation of the hydraulic system. If you rely too much on these operations, it will increase the cost of repeat repairs.

Long-Term System Optimization Strategies

Long-term optimization is the complete resolution of failures by improving design or overall debugging, rather than relying on frequent maintenance. Key practices include:

• Improving the oil’s ability to dissipate heat and controlling the oil temperature to prevent deterioration caused by excessive temperatures.
• Adjust the action sequence of the actuating elements, flow distribution, and pressure control methods.
• Adjust the matching relationship between pumps and valves, piping layout, and load to reduce internal leakage and pressure fluctuations.
• Enhancing piping support to reduce piping vibration and the risk of air intake.

All of these operations reduce the probability of failure by improving the design and the matching method between the various components, rather than maintaining operation through frequent repairs.

When to Involve a Professional Hydraulic Solution Provider？

When hydraulic problems are beyond the scope of single-point troubleshooting, if you continue to let your maintenance staff go blind, you’ll only extend downtime, increase the cost of repairs, and even face greater risks. That’s why you need to recognize when you should leave it to the professionals.

Clear Signs External Expertise Is Required

When the following occurs, it means that the problem is no longer suitable to continue to be dealt with by the maintenance personnel alone:

• Component replacement, venting, and parameter adjustment have been completed, but the fault still occurs or recurs in a different form.
• Unstable movement, pressure fluctuations, abnormal noise, and system heating occur at the same time and cannot be clearly localized to a single component.
• You need to reevaluate the circuit design, piping layout, or control logic, and the maintenance staff lacks system design experience or analytical tools.
• Each trial and error results in a significant loss of production, and the cost of continuing to let your staff troubleshoot is already higher than bringing in professional support.

What Information to Prepare Before Contacting a Supplier？

Before contacting a professional provider, you need to prepare sufficient information to shorten the time of diagnosis and reduce the cost of communication, and it will also help you determine whether the person is truly professional.

You need to prepare the following basic information:

• System schematic or circuit diagram
• Pump, valve, and actuator models and specifications
• Data on pressure, flow, and oil temperature under normal and abnormal operating conditions
• Details of the occurrence of faults
• Recently replaced or adjusted parts
• Changes before and after the occurrence of faults
• Fluid testing or contamination

You can quickly determine whether the person is a professional by the way they ask questions:

A professional supplier will ask:

Under what circumstances did the failure occur?

Is the failure related to a change in load?

Have you repetitively repaired a component before?

Unprofessional suppliers often focus on:

Whether a valve or pump needs to be replaced.

He will recommend the product rather than understand the system.

If they are eager to sell components without first understanding the system structure and operating conditions, they will often only solve surface problems.

Preventing Recurring Hydraulic System Problems

If you want to prevent hydraulic system failures, you have to start at the design level and with maintenance strategies.

Design-Level Prevention

Many hydraulic systems fail because people only consider getting the system up and running when designing it, but don’t think about how to make the system run smoothly for a long time. There are a few common system design mistakes below::

In the selection of pumps and valves, only look at the rating, but the actual working conditions for a long time beyond the design boundary, resulting in internal leakage, heat, and shortened life of the system, and other problems.

The design does not take into account the frequent start and stop, shock, or multiple actuator switching, so that the pressure and flow continue to fluctuate.

If you design line lengths, diameters, and supports without considering the system’s fluctuating frequencies, the vibration and noise can easily be amplified.

If you don’t have a well-designed cooling system for your system, you’ll have to rely on frequent oil changes to alleviate the heat problem.

How can you reduce the probability of failure at the design stage?

You need to allow a reasonable performance margin for pumps and valves.

In the circuit design, you need to take into account the effect of load variations and action sequences on the system.

You need to lay out the piping wisely and secure it firmly so that it doesn’t vibrate too much.

Take good cooling measures so that the system does not run too hot.

Maintenance Practices That Actually Reduce Failure Rates

You should judge the condition of the system by the state of the fluid, changes in temperature and pressure, rather than replacing parts at fixed intervals.

You should focus on the trend of the parameters, not the data at a particular moment in time.

You should regularly check if air is mixing into the system and if there are serious internal leaks in the system.

You should fix the system in time when there are some minor problems.

FAQ

The hydraulic system has become noisy, but the pressure seems normal. Should I deal with it?

Yes. Noise is usually an early sign of an unstable system and can be related to air mixing, poor oil suction, or worn gears. If you don’t deal with it, it can easily lead to a loss of system efficiency later.

Is it a fault if the oil temperature is high but not yet above the alarm value?

It is an early failure. A high oil temperature indicates that system efficiency is decreasing, and continued operation will accelerate fluid and component deterioration.

Is it worth troubleshooting the problem if the system jerks occasionally, but is normal most of the time?

Yes, it is. The system may shake occasionally due to air mixing, pressure fluctuations, etc. The cost of troubleshooting at this time is the lowest.

Are there any easily overlooked signs of internal leakage in its early stages?

Common signals include: oil getting hotter slowly, the system using more energy, and the need to turn up the pressure a lot to finish the action.

Why is it that some system parameters seem to be within normal limits, but the equipment just doesn’t work well?

Because one part of a system is working normally doesn’t mean the other parts are working well together. If the system doesn’t work well together, is unstable, or doesn’t fit the loop, it can still be inefficient.

What changes would make the biggest difference without replacing the whole system?

The most effective solutions are often to optimise suction and return lines, prevent air from entering, reduce unnecessary throttling and internal leakage, and adjust the pump-valve fit.

Final Thoughts

Hydraulic system problems are often caused by more than one thing going wrong. It’s usually a mix of issues with the flow, pressure, temperature, and how well the parts fit together. If you can work out how bad the problem is, find the main issues, and make the right changes, you won’t have to fix it again. Target Hydraulics has been analysing hydraulic system failures and making them better for more than 10 years. We can help you find the reason for system failures, design better circuits, and make your system more stable. If you keep having the same problems with your system, contact us for a better solution.