What to Check if Your Hydraulic System is not Working

When a hydraulic system stops working as intended, whether it is due to a major leak or a failing pump, it can bring productivity to a grinding halt (both literally and figuratively). The process of tracking down the source of the problem involves troubleshooting, which takes considerable skill, experience, and common sense. However, there are some valid guidelines and good hints to help with the process.

Preparing for Troubleshooting

The first step in effective troubleshooting is making sure you understand what the problem is — and this can involve asking quite a few questions. If someone says, for example, “The pump is vibrating really bad” then you need to delve a bit deeper with questions, such as:

hydraulic pump strainer maintenance
  • How long has this been going on or when did it start?
  • What was going on when you first noticed it? (e.g., system startup or shut down, heavy load, drastic temperature change)
  • Have there been any recent changes to the system, such as maintenance, modifications to the settings, or repairs?
  • When was maintenance last performed?

Once you have gathered all the facts that you can, it’s time to pull the hydraulic schematics for reference — do not attempt troubleshooting without this! The schematics provide valuable information about flow and pressure in the system.

Common Problems

There are certain problems commonly prevent hydraulic systems from working properly, such as an inoperative system or overheating hydraulic fluid. What follows are some troubleshooting tips for typical issues that arise in hydraulic systems.

System Inoperative

If the hydraulic system is inoperative, there are several things that can be checked. Verify the hydraulic fluid levels and keep in mind that leaks can lead to significant loss of hydraulic fluid. Take a look at the hydraulic filters, because if they are dirty or clogged badly enough, it can seriously impact performance. Check for restrictions in the hydraulic lines; restrictions often take the form of a collapsed or clogged line.

Make sure there are no air leaks in the pump suction line. Also inspect the pump itself; if it is worn, dirty, or out of alignment, it will affect system performance. The pump drive can be a source of issues if it the belts or couplings are slipping or broken. It may be time to replace some components; as they begin to wear, it can lead to internal leakage. It is also a good idea to make sure that the unit is operating within its maximum load limits.

Slow Operation

improve hydraulic system reliability

When a hydraulic system begins working more slowly than normal, one of the causes can be hydraulic fluid that is too thick, which may be due to cold temperatures or the use of an inappropriate hydraulic fluid. Air trapped in the system can be a problem, as well as restrictions in the line, due to dirty hydraulic filters. Another potential issue is badly worn hydraulic components such as pumps, motors, cylinders, and valves.

Erratic Operation

If the system is operating in an erratic, unpredictable manner, the most common causes are air trapped in the system, hydraulic fluid that is too cold (which means the equipment needs an opportunity to warm up before use), and damaged internal components such as bearings and gears.

Excessive Noise or Vibration

Another common issue with hydraulic systems is excessive/abnormal noise or vibration. If it is the pump that is noisy, then check that the oil level is sufficient, the correct type of fluid is being used, and that the oil is not foamy. If the oil is foamy, that points to air in the fluid which can lead to cavitation and expensive damage. It is also wise to verify that the inlet screen and suction line are not plugged. For both pumps and hydraulic motors, there can also be internal issues, namely worn or misaligned bearings. And do not forget to make sure that the couplings are secure and tight. Keep in mind that pipes and pipe clamps can vibrate if they are not secured properly.

Overheating Hydraulic Fluid

Fireproof hydraulic power unit

Excessive heat is never a good sign in a hydraulic system and often leads to a system working at sub-optimal levels. One of the purposes of hydraulic fluid is to dissipate generated heat, but the system should not be generating enough heat to cause the fluid to reach high temperatures.

There can be a host of causes behind hot hydraulic fluid, starting with contaminated hydraulic fluid or fluid levels that are too low. There may be oil passing through the relief valve for too long at a time; in this case, the control valve should be set to neutral when it is not in use. Worn out components within the system can also lead to excessive temperatures due to internal leakage.

If there are restrictions in the line or dirty filters, hot hydraulic fluid will result. If hydraulic fluid viscosity is too low, it can lead to overheating as well. Finally, there may be a need to make sure that the oil cooler is functioning correctly and that the key components are clean enough for heat to radiate away from them.

Low Viscosity

We have discussed low viscosity as a symptom, but it also qualifies as its own problem. When trying to determine why the fluid is not as viscous as it should be, the three things that need to be checked are damage to the oil (often from extreme temperatures or aging), use of the wrong type of hydraulic oil, or the presence of water in the hydraulic fluid. In all three cases, the system will need to be flushed and the oil replaced.


hydraulic hose leak

Even a small leak over time can lead to enough fluid loss to impact performance, and if fluid can make its way out of the system then damaging contaminants can make their way in. Most leaks are the result of worn out seals, damaged hydraulic lines, or bad connections. Looking for the source of a leak can be challenging and dangerous. Never try to locate a leak using your hand when the system is running because the high pressure hydraulic fluid can puncture your skin and get trapped beneath, leading to what is known as an injection injury. A quick and safe way to detect leaks is to use cardboard or plywood instead of your hand. If the leak is coming from a motor or pump, then the likely cause is a worn-out seal or gasket that needs replacement.

No Fluid Flow

Having no flow within the hydraulic system is a serious issue that can have several different sources. The first step is to determine exactly where the fluid flow stops, such as failure of the pump to receive fluid at the inlet (usually the result of a clogged line or dirty strainers) or a failure for fluid to exit the outlet, which could be due to a pump motor that needs replacing, a sheared coupling between the pump and drive, or a pump/drive failure. It would also be a good idea to make sure the pump rotation is set correctly and the directional valves are in the correct position. The most expensive problem would be a damaged pump that needs to be replaced or repaired.


The first step in troubleshooting is to gather as much information about the problem as possible and then pull the hydraulic schematics for the system. From there, you basically follow a process of elimination until the root of the problem is uncovered. Something else to keep in mind with regard to troubleshooting, however, is that once you have tracked down the source of a problem, it may lead you to yet another problem that will need some troubleshooting. Getting your hydraulic system back in working order can be a time consuming process.

For example, you may uncover that the cause of overheating hydraulic fluid is low viscosity — but why is the fluid insufficiently viscous? The troubleshooting process is not over until that issue is uncovered. Take, as another example, the case of a pump whose internal components have worn out and affected overall system performance — why did the components prematurely wear? It may be a cause of misalignment, insufficient lubrication, or contaminated fluid. A good hydraulics technician will not just track down and address the problem, but will keep troubleshooting to make sure that the problem does not happen again.

MAC Hydraulics

At MAC Hydraulics, we understand the importance of having a functional, efficient hydraulic system. We know that any downtime costs money and time that your company simply does not have to spare. That is why we offer comprehensive hydraulic services that include 24-hour emergency on-site troubleshooting and repair services. Our team of experienced hydraulics experts can work on motors, pumps, valves, cylinders, and systems. We serve a wide range of industries, including everything from paper and pulp processing to aerospace to construction equipment. When complex repairs are called for, we have a full machining center and certified welders. We also offer customized maintenance plans tailored to your needs and your equipment. Contact us today to find out how MAC Hydraulics can help keep your hydraulic systems operating at peak efficiency and productivity.