I lost power steering, brakes 3 pt., and all other hydrlics, this happened all of a sudden. Any opinions or insight from past problems? I was thinking it was a pop off valve but I dont know where it is or which pump it is.

Those are all run from the main pump in front of the engine. Is the pump coupler good?? They do strip out if the have a lot of hours on them, especially if the clamp bolts loosen some.

Filters Clean? Another possible is a clogged suction strainer, its in the bottom of the trans case. On power shift, on the right side, just in front of the axle planetary. (Drain the trans before checking) Quad might be in the same place??

A pressure relief might have gotten stuck open, dumping your pressure.


Sudden operation (pressure) loss like that, I would suspect bad pump coupler. It might be worth removing the coupler for an inspection.

it partaly works right after fire up put poorly

Fluid level, filters, pump might need a rebuild. How many hours on the pump, how good of maintenance? Hook up an emplement with rotten or potentially dirty lines lately? First I'd do is change external filter(s). I don't know on a 4020, but some JDs have a screen in the system somewhere. Not sure if it's under a line coming off the pump, or near the rear of the tractor. That's why my dad has Service & Technical Manuals.

it happened all at once there wasnt any thing leading up to it like a filter. it partily works for aprox. 30 sec. then fails totaly.

I think its the pickup screen, my dad drove around in the 5500 with a brake dragging and filled the trans with brake material and it did the same. The stuff would fall off the screen when it wasnt running and the hydraulics would work when you first used it but once the fluid was moving the material got sucked onto the screen.

good call on the pickup screen i agree.