Yes, the pictures help a lot. We now know that your loader has a typical FEL control valve with what looks to be a power beyond port taking flow to the 3pt. Yours not having the rear remotes does simplify things.
To answer your questions best as I can.....That's clever to listen to the return that way and I'm not surprised you would hear the returning fluid when listening through the full cap. My guess is what you hear seems normal, especially since the return noise should stop when you work the loader and it does. The rest of the noise?? The bubbling?? Well, I am not surprised that there is some suction side air leak in 30 year old hoses, but my guess from the other things you've saidis that any suction leak is not the main cause of the loader being so slow.
Yes, lots of guesses here.
On the curl and raise not working simultaneously - that one is easy. Separating the functions is common when a manufacturer specifies an inexpensive loader control valve. Coupling the functions requires a more complex casting and additional machine work on the spools. So separate functions like you have ust means Quickie Loaders used a generic control valve instead of a more expensive one made to match your tractor. flow You can replace that valve with a better one that will bolt right up someday if you want. A better one will allow feathering both motions at once, and the best valves may also have some degree of internal fluid regeneration - which really does speeds up a loader.
All in all, some small part of the slowness is probably due to that control valve, but the valve shouldn't be slowing motion as much as yours does.
The photos are great! Now we can make some educated guesses, but because yours has power steering we probably still need the hydraulic schematic in the workshop manual for the Kubota
M5400, do you have that manual? I can't seem to find one free online. The place I found the operator's manual - attached to post #22 - doesn't have a workshop manual.
However, there is an active market in old manuals on Ebay. Take a look there. The best are the factory workshop manuals - usually in printed form.
Any info we can get from Quickie Loaders about the model 310 loader and Kubota hookup would help too.
1st Photo:
Line 1 is the "P" or pressure line coming either from the hydraulic pump...OR from one side of a priority valve that separates the main hydraulic pump flow into a power steering flow that has priority and then the remaining flow goes to everything else.
Line 2 is the return to the "T" sump or Tank.
Line 3 is the power beyond that goes back to the 3pt. If we could see the side of the valve casting there should be a raised "PB" there. You should trace all these lines to confirm.
NOTE: IF LINES 1 & 3 ARE REVERSED into the Control valve, that could cause the loader to be slow. So be sure to trace those lines !
2nd Photo. Not sure what view this is. What are we looking at?
3rd Photo. From underneath? #2 should be going to the tank sump, but is it? I see some splits in that old hose where it bends, but if it is return to tank, those don't matter.
Is the steel line the suction line from sump tank to your filter?
What is the unnumbered hose?
Now we are getting somewhere.
rScotty
