Hey guys, I'm working on CT322 for a friend and don't have much experience in heavy equipment. A little backstory: he had let a concrete company use it while he was away. The machine developed a leak, and they continued to use it until the left side hydrostatic motor had failed, running metal throughout the system. He had me install a used motor and flush the system out. The machine drives, but the pump whines loudly, and the bucket will only operate at full throttle. I put a gauge on the lower aux coupler and had 300psi at idle that went to 490psi at full throttle. The spec I found says it should be at 3450psi at the coupler. I can't find any diagnostic procedure. Are there valves or solenoids that I should be checking, or is this as simple as a bad pump? (This company did continue to try to move it with no fluid for a long time.)
Metal contamination from a failed hydrostatic motor almost certainly destroyed more than just that motor - you're dealing with systemic damage. Just replacing the pump won't fix this - contamination will kill the new pump immediately. Your friend needs to understand this isn't a $500 fix anymore; running it after the leak caused $10K+ in damage. Your 490 psi vs. 3450 psi spec confirms the pump is severely damaged (worn internally or the compensator is stuck/failed). But here's the critical issue: You cannot just flush and hope - metal particles likely to be embed in Main control valve spools (causing sticking/bypass), Pump compensator and servo pistons, All other motors, cylinders, relief valves, Cooler passages too. The loud pump whine = cavitation or severe internal wear slippage. Combined with no pressure, the pump is toast. Reality check : After catastrophic metal contamination, proper repair requires. Complete system teardown : pump, valve block, all motors, cylinders disassembled and inspected. Replace hydraulic oil filter housing (metal embeds in filter media housing). Flush coolers with solvent, replace all hoses. New pump, rebuild valve block Don't install a new pump without full system remediation.