OK. That type of oil reservoir tells us something. If it is what I think it is, that Kubota is using a popular aftermarket way to run a loader on some very small compact tractors of the 1970s and 80s.
I had the same oil in the loader frame setup on our 16 hp Yanmar. It was considered to be a lot better than using the tractors internal 3pt hydaulics.
On those systems there was an add-on hydraulic pump just for the loader. The add-on pump was either driven off the front of the engine on a flex coupling to the front engine pulley..... or off the PTO in the rear.
The ones on the front were a very universal type of pump - in fact the whole system used simple universal industrial parts. So if it has gone bad it is very easy to replace from one of the online suppliers of such pumps like surpluscenter.com
Most of those systems with the oil in the loader upright did not have a filter at all. Just a screen at the bottom. You basically change the oil by disconnecting the suction hose at the bottom on the oil reservoir. Changing it and checking the hoses wouldn't hurt. The oil itself is any light weight trans/hydraulic oil. John Deere HyGard low viscosity (winter) is what many use.
Yes, the gauge on the T fitting will tell you a lot. Remember that a hydraulic system will only develop pressure in response and in proportion to resistance. For example if you are not lifting anything, expect that there will be flow but not much pressure.
If the system only needs to develop 800 psi to lift whatever is in the bucket then that is all it will do. I rarely see over 1200 psi on mine. If stalled, it will go to max pressure setting. That is adjustable via the relief valve and most are in the 1800 to 2800 psi range.
Sure, it could have pressure and not volume if there was some restriction on motion or fluid blockage. Easy way to test that is just put light motor oil in the upright and keep pouring it in while you run whatever hose you suspect into a 5 gallon bucket. Volume & velocity is fairly low at 3 gpm. Do at idle & you'll know in 15 to 30 seconds. Try not to run it dry. First try would be with the hose that connects the output of the pump to the input (IN) port on the control valve.
That front mounted pump system and oil in the upright was actually a pretty nice system.
Luck,
rScotty
