If a hydraulic pump is producing a noisy whine when in operation, the cause may be __________.

Correct Answer: Option A — an air leak in the pump suction line above the oil level in the reservoir

A noisy, whining pump is a classic symptom of cavitation caused by air entering the suction line. Air leaks above the oil level in the reservoir allow atmospheric air to be drawn into the pump, causing erratic operation, vibration, and potential mechanical failure of the pump's internal rotating elements.