How to Troubleshoot a Hydraulic Pump

by G.K. Bayne

Hydraulic pumps are used not only in heavy industry but can also be found around the home. Many riding lawnmowers as well as log splitters will use the motor-driven fluid pump. The hydraulic pump in its most basic form moves fluid from a low pressure, called the suction, into a potential high pressure, or the discharge. The high pressure is created by any resistance of flow. Resistance of flow is caused by the closing of actuation valves and a clogged or blocked system. Many factors dictate the efficient use of the pump for performing its task. By following a set process you can troubleshoot the hydraulic pump from one end to the other.

Check the condition of the hydraulic oil filter. These filters are typically placed on the low-pressure discharge end of the system. After the high-pressure fluid has done its work, it exits from a hydraulic motor or cylinder, then passes through a screw-on type filter. Another filter to check is the suction screen filter. This metal screen is composed of finely sized holes on a steel screen. Small particles that could collect in the metal tank reservoir are caught before entering the pump. If these two filters are clogged they will cause pressure problems in the pump.

Test the operation of the pressure relief bypass valve. Attach a pressure gauge to the pressure relief valve port. Use the Allen wrenches to remove the setscrew plug. Insert the gauge and tighten with the end wrench. Turn the system on and confirm the correct setting of the relief valve. The pressure gauge should not register any fluid pressure if the valve is set correctly. A low setting on the valve will cause fluid to bypass the main hydraulic system and exit into the reservoir tank.

Read the fluid's temperature with the tank thermometer. Hot hydraulic fluid can cause burning or scorching of the seals inside the pump. High fluid temperature may indicate a bypassing of the pumps' seals. Some hydraulic systems may also employ a radiator type device for cooling the fluid that sets inside the reservoir tank. A separate circulation pump is used to move the fluid through the radiator.

Inspect all pump seals and bearings. A slight leak at a bearing position and seal will indicate that there is a problem with the pump. The leak can last a long time before imminent pump failure occurs. Typically a leaky seal is an indication that a bearing is failing, either in the pump itself or the motor driving the pump.

Check individual system components with an infrared thermometer. What may be perceived as a pump problem may be another component. Heat is created by the bypassing of fluid through an individual actuator or cylinder. Test all components for excessive heat during the operation of the hydraulic system.


  • check Change the hydraulic fluid or oil according to the manufacturer's recommended time frame. Poor viscosity can create internal problems to the pump such as premature wear to all metal parts.

Items you will need


About the Author

This article was written by the It Still Runs team, copy edited and fact checked through a multi-point auditing system, in efforts to ensure our readers only receive the best information. To submit your questions or ideas, or to simply learn more about It Still Runs, contact us.

More Articles