hydraulic problems on david brown 990

dlawson · Sep 15, 2013

i have a 1972 david brown 990 with a case loader .loader works excellant but can not use 3 point hitch because if arms are raised i can hear the releif valve on pump and oil starts leaking out of return line from loader control valve

Bret4207 · Sep 16, 2013

Do you have a 3 way valve body on it? It's a valve body on the upper front of the rear ax that would be sort of under your left thigh as you sit in the seat.

dlawson · Sep 16, 2013

No three way valve loader is fed from a block under valve for
rear remote cylinder beside drivers.right leg behind lever for lift
arms

Bret4207 · Sep 17, 2013

RG Martin is the guy here I'd look for a response from. I got no more ideas as I'm not familiar enough to guess.

RGMartin · Sep 17, 2013

Buried in projects up to my chin(Corn needs to come off soon, wheat needs to go in, lots of old worn out equipment needs TLC to do the job). Not as much internet time.

See if I follow what you are saying, if you raise the 3 point arms, they go all the way up, no matter what you do to the lever(including blowing the relief valve)? If you shut the tractor down with them in the up position, do the arms respond properly to the lever on the way down?

If the above is true, it sounds like a stuck "Latching Valve" in the Selectamatic valve body. It is a low dollar fix(some gasket material and 1500 grit paper), but will take at least 3-4 hours to pull the valve to fix the problem.

dlawson · Sep 17, 2013

Arms will go down with lever but you have hold lever down till arms are all the way down or lever will come back up.lever also creeps back up on its own

RGMartin · Sep 18, 2013

Still not sure on how your loader is plumbed, I have seen these set up so many different ways... Pictures would help.

Is the loader valve open or closed center? Has the system ever worked right?

The lever creeping back it probably just the friction brake on it. The lever all the way back is the "Select" position, normally there is spring to keep it from going all the way back unless you push it there. The relief valve will normally squeal once the arms are all the way up and valve in "select". "Select" allows the lift to go a hair higher than normal so that you can change the mode on the little 3 position lever from "height", to "depth", and "TCU" function.

The brake for the 3 point lever is adjusted by the 2 nuts on the side of the housing near your right heel. They take a 3/4" wrench. Loosen the jam nut, the snug the inner one till you are happy, then jam the out back down.

dlawson · Sep 20, 2013

Plumbing for loader

dlawson · Sep 20, 2013

have only owned tractor for 2 years three point has never worked right in that time,have been told it worked before that ,but can not be sure load is plumbed into block on top of control valve for outlets at rear of tractor not sure wehter loader valve is open centre or closed,the basic problem is that i am not able to use three point hitch beacaue when i bring lift arm lever up arm(not in to spring loaded part at top just normal operating area releif valve blows will also do the same if i lock the lift arms in up position

hydraulic problems on david brown 990

dlawson

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