KX121-3 Hydraulic troubles

[uffex]

hi Travis indeed the dozer should work irrespective if you have servo pressure or not.

 

[Travis Lohnes]

Right, the dozer does not move, nothing will move.

 

[uffex]

Ok that could be main relief lodged open or main pump defect, any strange noise from the pump - any witness stuff in the filters?
Kind regards
Uffex

 

[Travis Lohnes]

Small pilot filter was really dirty, I just found out it was there and judging how bad it was previous owners didn't change it either. I do not hear any strange noises. I'm not sure how to test the pump.

I removed control valve main relief and everything seemed OK but I'm not positive.

 

[uffex]

Good day Travis
One possible cause came to mind however when this happened for me all functions worked but very slowly, you have a small 0.7mm orifice in the load sensing line if this was obstructed it would prevent the pump from coming off minimum flow. You can see this in the schematic at the very end of the MCV.
Kind regards
Uffex

 

[Travis Lohnes]

Good day,

I had that orfice out, cleaned it and no difference. I installed a gauge on the bottom of the MCV to see pressure on that load sensing and the gauge didn't show any signs of pressure.

 

[uffex]

Good day
The pressure would only show up when you used a function if that was the case it points more to the main pump - drive failure or pump defect.
Kind regards
Uffex

 

[Travis Lohnes]

That's where I'm beginning to believe my problem is also. With no operator function being used would my main pump probably have some pressure? Should it have "standby pressure" of approx 400 psi , the setting of relief valve " a3 " on the schematic?

 

[uffex]

Good day Travis
Before we condemn the pump just make sure the high pressure valve in the inlet section is not lodged open.
Kind regards
Uffex

 

[Travis Lohnes]

I'll check that again tomorrow, had it out before and it appeared to be OK but I'll have another look. What about the main relief on the outlet valve? Could that one be an issue?

 

[uffex]

good day Travis
Main relief (A3) is a possibilty you should have stand by pressure at port "P", check out the main relif first and then if you have no stand by pressure we are back to the pump.
Kind regards
Uffex

 

[Travis Lohnes]

I had a3 off the inlet and a1 off the outlet valve. Can not see anything wrong with either. I removed P line from inlet valve and blew air into the valve. With the return lines removed I get some air coming out of the outlet valve at the tank line. I assume the air would have to be bypassing the relief a1 to be coming out on the tank line. I'm not sure if this is a sure sign of a1 relief trouble..?

 

[Travis Lohnes]

Oh, disregard my last post. I read of my manual more and I believe that a1 main relief on the outlet should in fact have slight bypass on low pressure passage, it does not go right to tank, it goes to the oil cooler.

 

[bmd1987]

I know this is an older post but Just curious what the diagnosis ended up being? I have the same machine with the same exact symptoms ive been fighting intermittently for some time.

 

[bc_outpost]

I realize this is an old post but thought I could jump in as I am just curious if hyd. pump failures are common on the 121-3 machines. I am aware of two local owners that have had what I would consider premature failures at between 22 and 25 hundred hours. The machines were from the 2007 era.