1979-1980 Ford 3600 Diesel with Hydraulic Problem. Details Are Below In The Notes?

I have a 1979-1980 Ford 3600 3cyl diesel with a Lehr/Farmhand 22 loader.

The loader worked without any problems what-so-ever before parking it in back in November for the Winter months. Now that it's March & we got a 55 degree day, I wanted to start up the tractor and get some routine maintenance done it… But even thou the tractor started right up, nothing happens when I push or pull either spool valve handle for the loader. I tried the selector valve that pulls in and out that's located below the right hand side of the seat which faces the hi/lo shifter but whether it's in or out didn't make a difference… This is the valve that diverts flow from the 3pt arms to the loader, and when it's pushed in my 3pt arms work like they should and when it's pulled out they don't work and so I know that it has to be pulled all they way out or in the middle for the loader to work. I checked the hydraulic pump and it's still full. I looked all around the under side of the tractor and the ground but there's no leaks.

Is it possible to get moisture in the hydraulic system and it froze up and won't let the hydraulic fluid circulate or something?

Can it be a valve or plug that needs to be removed for having bleed the air out?

Does the pump need primed and if so, how is it done properly?

Any help would be appreciated! Over the years I have become familiar with working on 1960-70's Cub Cadets and 9n/8n tractors but this is my first time owning a newer Ford tractor and a loader.

Check the output pressure at the hyd pump. Coupler could have sheared, pump has failed or there's a supply line issue to the pump. Engine off, loosen the supply line fitting to the pump. If hyd fluid comes out, fluid supply is good.

If there were no issues like that before you put it away for the winter, I'd say it is something simple. Like the divider valve is not moving completely. Frozen condensation could be a possibility, but letting the tractor run for an hour or so in a 55 degree day should rule that out. Make absolutely sure the system is full of oil. Does it have a hydraulic filter that could need changed? Just exempt all the easy things before getting too carried away.

Here is the picture of the selector valve that's located between the seat and the hi/lo shifter. The selector valve is for diverting hydraulic flow from the 3pt arms to the auxiliary output for the loader

Sounds like the selector valve may have a problem diverting pressure to the loader lines… Bad valve, seals, etc… May need to take it apart and clean it out… Reseal. Does it make any noise as if it's trying to lift the loader bucket when operating it in that mode? Is the bucket frozen in the ground? You might also try loosening the fluid lines to the loader on the extend side of the piston/cylinder and see if you get any fluid pressure from it when operating the bucket function. If you do get good pressure for both, then both the pistons/cylinders may be leaking internally. Not common for both to bad at once… Seems more like a bad diverter/selector valve issue since you do get 3pt function.