Flow instability, often accompanied by pressure fluctuations, is frequently related to issues within the control piston mechanism. This can be due to contamination scratching the control piston, a weak or damaged control amplifier spring, or other damaged components. Addressing this usually requires disassembling the pump to inspect, repair, or replace the affected parts, and possibly increasing damping or spring stiffness.

External leaks can originate from:

• Shaft Seal: Damaged or worn-out shaft seal
• Pipe Connections: Loose hose connections, damaged fittings, or aged/cracked sealing washers
• Case Ports: Leaks from the variable mechanism cover bolts due to loose bolts or seals
• Case Imperfections: Rarely, sand holes in cast iron casings or poor welds
• High Case Pressure: Excessive internal leakage can pressurize the case, damaging seals or pushing them out. Ensure the case drain line is unrestricted, of adequate size, and not too long

Bearing flushing is recommended for: using special HF fluids, operating at viscosity/temperature limits, or for pumps installed vertically (shaft up). Refer to technical documentation for specific flow rates, which range from ~3 L/min for size 40 to ~40 L/min for size 1000.