In troubleshooting a hydraulic circuit with a noisy pump which of the following is not a likely cause of the trouble?

In troubleshooting a hydraulic circuit with a noisy pump which of the following is not a likely cause of the trouble?

• A. Air Entering Pump Inlet
• B. Misalignment Of Pump And Drive Unit
• C. Pressure Relief Valve Set Too Low
• D. Dirty Inlet Strainer

Answer: (B)

Noisy pump symptoms in a hydraulic circuit usually point to issues that affect the suction side or the valve behavior, rather than the drive train. When air gets into the pump inlet, it forms bubbles that collapse inside the impeller, causing a loud cavitation noise and reduced flow. A dirty inlet strainer has a similar effect by restricting flow and promoting cavitation or turbulent flow near the impeller, which also produces noise. If the pressure relief valve is set too low, fluid is bypassed back to the tank or nowhere near the intended pressure, and the high-velocity flow through the valve can generate a noticeable chattering or whining sound. Misalignment between the pump and its drive unit tends to produce mechanical issues—vibration, wobble, and wear in couplings or bearings—rather than the hydraulic-side noise described. It can cause overall drive train problems, but the characteristic pump noise from cavitation or valve flow is not the primary symptom of misalignment.

Noisy pump symptoms in a hydraulic circuit usually point to issues that affect the suction side or the valve behavior, rather than the drive train. When air gets into the pump inlet, it forms bubbles that collapse inside the impeller, causing a loud cavitation noise and reduced flow. A dirty inlet strainer has a similar effect by restricting flow and promoting cavitation or turbulent flow near the impeller, which also produces noise. If the pressure relief valve is set too low, fluid is bypassed back to the tank or nowhere near the intended pressure, and the high-velocity flow through the valve can generate a noticeable chattering or whining sound.

Misalignment between the pump and its drive unit tends to produce mechanical issues—vibration, wobble, and wear in couplings or bearings—rather than the hydraulic-side noise described. It can cause overall drive train problems, but the characteristic pump noise from cavitation or valve flow is not the primary symptom of misalignment.