Wow, this is another variations of hydraulics that I have never seen before on an IH 424.
Could you check that the steel hydraulic pipes that connect under the seat goes to the suction(larges pipe) on the pump mounted in the front of the radiator on the tractor?
The larger rubber hose (return line) should come from the loader hydraulic control valves?
Using this method to connect a 2000 loader using a front mounted pump, the transmission and differential is used as the hydraulic reservoir for the loader.
The Industrial 2424 model has a dipstick up by the dash on top of the transmission case, yours does not appear to have the dipstick so proper hydraulic oil in the transmission is checked by the pipe plug beside the gear shift lever, the lever should be within 6" of the fill plug, use CIH Hytran or equivalent.
The 3pt/power steering normally uses the hydraulic reservoir under the seat and it is filled from the pipe plug behind the seat and proper level is when you look in the fill hole you should see like a shelf down in the reservoir and full is when the shelf is covered. If you have drained this reservoir or ran it low do to a broken hydraulic line you may have to fill the reservoir in stages, fill to proper lever, put filler plug in about 2 turns start tractor and work 3pt and power steering, stop tractor, open filler plug slowly to let out air, refill and repeat procedure until reservoir is correct level.
Is that round cylinder container mount at bottom of the dash a hydraulic filter?
I assume that ball valve has been installed because the hydraulic splitter for the 3pt and power steering stopped working?
I require some more pictures from the right front engine pump hydraulic pipes going back to ball valve to completely understand this hydraulic setup.
PS, the 424 has a very simple hydraulic system called Open Center hydraulics where the pump is constantly pumping hydraulic oil in a loop - from reservoir into the suction line (large line) thru the pump and out the high pressure line(small line) thru the hydraulic valves and back to the reservoir. When a hydraulic valve is opened then the hydraulic oil is diverted to a hydraulic cylinder.