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Troubleshooting Hints For Hydraulic Systems - Part 1

By R Allen  –  Published 10/20/2008

Noisy Pump

  1. Low fluid level in reservoir, air entering system; Fill reservoir to proper level.
  2. Leaking fittings, hose and tube connections on inlet side of pump, allowing air to enter system.  Use system compatible grease or oil to coat the fitting/connection suspected of leaking (while system is running).  Pump should quiet momentarily after application if connection is leaking.
  3. Inspect suction strainers for cleanliness.  Clogged strainers or obstruction in suction line will likely cause pump cavitation and severe pump damage.

Low System Pressure

  1. Relief valve setting too low.  Relief valve may have been re-adjusted.  If setting is too low, fluid will be diverted back to reservoir, resulting in heat build-up and low system pressure, re-adjust relief valve to proper setting.
  2. Worn or damaged pump or actuators.  Plug work ports at power unit and check pressure.  If relief valve is set properly and pressure is still low, the pump most likely needs repair.  If pressure is normal, isolate each actuator in the system one at a time to indentify the failing component.  Repair as needed.
  3. Unloading circuit malfunctioning.  If using a fixed displacement pump in conjunction with an unloading circuit, make sure circuit is functioning as intended.  Contamination, war or damage could cause unload vale to remain partially or completely open.  Inspect valve, repair/replace as necessary.
  4. Pump compensator set too low.  Variable displacement pumps with pressure compensation controls may have been re-adjusted.  Re-adjust compensator to proper setting; use care when adjusting compensator, the system relief valve may need re-adjusting to maintain a higher setting than the compensator (usually around 200 PSI higher than the compensator setting).

Erratic Operation

Valves, pistons, etc. are sticking or binding.  Inspect suspected part for mechanical deficiencies such as misalignment of shaft, worn bearings, etc.  Also look for signs of dirt, sludge, varnishes caused by fluid deterioration.


Relief Valve Stuck Open

Depressurize hydraulic system and remove valve.  Inspect for contamination and clean as needed.  Physically operate moving parts in valve to test for sticking or broken bias springs.  Replace if needed.

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