After draining all the fluid you may have to prime the pump by putting some hydraulic fluid into the input. As far as the slow loader, what's the position of your three point lever? If it's set to full up your hydraulic system may be in bypass. Back it off a tad. If that solves the problem your rock shaft probably needs adjusted. It is rare for the hydraulic pump to fail but it CAN happen.
Lets think about that. What happens in "full bypass"? You dont lose pressure at the loader. Just the opposite - the supply at the loader is maxed out at relief pressure.
The symptom reported was initially low pressure getting worse as the oil warmed up and now its no pressure at all. If that is accurate this is a pump or pump related problem. Pump fsilure is not uncommon - they all wear out. Age, contaminated oil, running dry, and/or running at excesdive pressure can and will kill a gear pump.
So time to step back and do a few simple tests. A good first step would be to take the oil delivery hose loose at the loader valve inlet snd check for flow and pressure. I think thats a LA351 so access should be pretty easy.
Testing flow is simple - put the end of the hose in the hydraulic filler and start the tractor. You should have a good garden hose supply coming out of the hose. If no flow then you can try coaxing the pump to prime with a slug of oil poured into the inlet port. If it wont prime there is a good chance its worn out.
Once ypu have flow testing the pump output pressure is a bit trickier. Its not clear to me where the main pressure relief is located.
Dan
