Product Overview Excavator Rexroth A8VO225 Hydraulic Main Piston Pump for Doosan DX500-9, DX520-9, DX530 (400914-00366), Sany SY485, SY550 (60008150), and Hyundai R520LC-9, R550 (31KB-10030). Heavy duty construction for mining applications. New and remanufactured units are available. Common Faults & Diagnostics Insufficient pump pressure & slow operation — Wear of piston, cylinder block and valve plate, excessive internal leakage. Weak operation & speed drop during combined