A heavy-duty excavator is experiencing sluggish hydraulic performance and excessive noise, particularly during cold starts. Upon investigation, the technician notes foaming and a strong, acrid odour in the hydraulic fluid reservoir. Which of the following is the most likely cause of these symptoms?

Question: A heavy-duty excavator is experiencing sluggish hydraulic performance and excessive noise, particularly during cold starts. Upon investigation, the technician notes foaming and a strong, acrid odour in the hydraulic fluid reservoir. Which of the following is the most likely cause of these symptoms?

Answer options: ✅ Cavitation in the hydraulic pump, due to restricted suction line or low fluid level.

• An overheated hydraulic system caused by a faulty pressure relief valve.
• Degradation of the hydraulic fluid resulting in viscosity breakdown.
• External contamination of the hydraulic fluid with water, leading to emulsification.

Correct answer: Cavitation in the hydraulic pump, due to restricted suction line or low fluid level.

Explanation: Foaming, excessive noise (often described as 'gravelly' or 'marbles'), and sluggish performance are classic symptoms of cavitation in a hydraulic pump. Cavitation occurs when insufficient fluid is supplied to the pump inlet, causing vacuum pockets to form and collapse, damaging pump components and fluid.