Can you put the
hydraulic pump out of gear and see if the
lever for the outer circuits will then release, may be stopping
the engine will have the same effect, and with the engine stopped
you could push a piece of round close fitting wood into one of the external couplers to release a small amount of fluid, try this with all couplers just to release any pressure, keep yourself well clear of any potential oil coming out at high speed, KEEP ENGINE OFF when doing this.
There is also some kind of divert-er that controls what service gets the most oil, it can be set to give more to the outer circuits or the lifts, may be worth moving it to see what happens.there is also a function to lock the external circuit lever in a pumping position, are you sure no one physically locked the external circuit lever in either up or down position.
I know nothing of this tractor model, I had old Crystals and they were excellent for me, never had trouble, seems like these 33 20 / 3340 tractors are giving hydraulic issues, there is a current post on here where the lifts wont go up after the posters tractor heats, though the loader works on the front, and another that the lift wont go down on.
You say the lift leaver wont stay up and the lifts drop rapidly,
how do you get the lifts up at all if the lift lever wont stay up.
Have you also checked the oil level for the backend.
Regards, J
