I have a syncro 4620 that as soon as I turn the engine off, I can hear all the hydraulic fluid draining from the front reservoir back to the filter relief valve. My plungers were already jammed on another tractor, so today I took out a couple of them to see if that was indeed the case.
It’s more of a hassle than anything else as it takes several seconds to start up before the steering and hydraulics work. And when they do, they are intermittent for a while before it clears up. The 3pt shakes for several cycles and the wheels are slow to catch up with what the steering wheel is doing.
The check valve in the transmission can wear out, allowing hydraulic oil to flow back into the transmission (emptying the reservoir) when the transmission pump is not turning, that is, with the engine off or the clutch depressed.
Console tractors do not have the check valve below the transmission pump outlet line like older tractors. The check valve for console tractors is in the valve housing. If the housing is okay, it is easier to replace a worn valve than to go through the machining process.