lift slow to return

[BenKirby]

recently replaced a small leaky hydraulic sensor next to hydraulic the hydraulic filter. pumped out hydraulic reservoir with transfer pump and tried utilize lift with reservoir low of fluid to purge as much of the old fluid as possible. refilled the reservoir with john deere hydraulic oil and after a few hours of operation found as I actuated the lift pedal into the down position the lift came down very slowly and bogged down the engine. wondering what damage I might have down by trying to change hydraulic fluid with an inappropriate technique or maybe just a clogged valve or got air into the system. Machine is a 1997 Bobact 773C. Any advice would be much appreciated.

 

[Tazza]

I'm wondering what the JD hydraulic oil was. For your machine, it should be running heavier oil like engine oil, 15W40/20W50. Thin hydraulic oil will cause damage due to lack of lubrication in the pumps.
You said it ran fine for a few hours, i can't see a problem in your oil draining procedure causing this. Even the wrong oil i can't see making the arms lowering slower. Lift yes, not lower...
These sort if issues, slow lift/tilt operation when going downwards/no weight on them has been things like anti-cavitation valves coming loose and pluging up ports. This causes restrictions and bogs the system down and the engine, just like yours is doing. Could your aux hydraulics be stuck on?
Just a few ideas.

 

[BenKirby]

I'm wondering what the JD hydraulic oil was. For your machine, it should be running heavier oil like engine oil, 15W40/20W50. Thin hydraulic oil will cause damage due to lack of lubrication in the pumps.
You said it ran fine for a few hours, i can't see a problem in your oil draining procedure causing this. Even the wrong oil i can't see making the arms lowering slower. Lift yes, not lower...
These sort if issues, slow lift/tilt operation when going downwards/no weight on them has been things like anti-cavitation valves coming loose and pluging up ports. This causes restrictions and bogs the system down and the engine, just like yours is doing. Could your aux hydraulics be stuck on?
Just a few ideas.

how would I check the anti-cavitation valves? Would this cause a leak in the system? Somehow the hydraulic fluid is getting on the engine block and causing it to smoke, but I can't see any apparent leaks and when I lift the cab to make observations the bics disables the hydraulic controls.

 

[Tazza]

how would I check the anti-cavitation valves? Would this cause a leak in the system? Somehow the hydraulic fluid is getting on the engine block and causing it to smoke, but I can't see any apparent leaks and when I lift the cab to make observations the bics disables the hydraulic controls.

The anti-cavitation valves are generally in the fittings on the control block i believe. They really can be anywhere... I know that's not really helpful, i don't have the same machine so i can't look it up for you.
Oil dripping on the engine would have to be coming from something higher up like the oil cooler? does your machine have a hydraulically driven cooling fan? it may be leaking too.