B2910 rear auxiliary block and spool valve help

[B leever]

Hello, I recently plumbed my 3 spool valve to the rear auxiliary block on my B2910 and I've got something wrong. The cylinders extend but I have to bump the control lever to make them retract. I'm sure I've plumbed something backwards. The spool valve has 3 ports labeled "In", "Out" and "PB".
Currently (I think), I have "In" connected to the top port of the Aux Block, "PB" to the bottom port of the Aux Block and "Out" is teed to the tank return located mid tractor where it's shared by the loader tank return.
Any and all help is appreciated.

 

[Russell King]

Did you have any other hydraulic equipment on the tractor (FEL, Backhoe…).

This is usually covered in the operator’s manual so I suggest you get one if you don’t have one already. Try this link (they are free but they request a donation to help keep site alive)

Index of Kubotabooks/Tractor Owners Manuals/

Look through the index carefully for your tractor model. I saw the Work Shop Manual (WSM) and an unidentified item that were for your model. I think either would have the information you need.

The general idea is that the OUT port of the tractor connects to the P port on the valve. The PB port then connects back to the tractor IN port. Then the Tank Return port on the valve can be attached to the Tee as you describe.

It actually sounds like the operation is correct IF you have a double acting cylinder attached to your new valve. The spool is moved by the lever to build pressure on one side of the cylinder and fluid is pushed in one side of the cylinder and out of the other side with little pressure into the tank return. When you release the lever the cylinder is basically locked since there is “no” flow into or out of either side of the cylinder so the piston in the cylinder can NOT move. Pulling or pushing the valve’s lever the other direction will the move fluid into the other side of the cylinder and low pressure fluid is pushed out the other side so the cylinder ram moves again. One way the lever is moved should extend the ram the other direction will retract it.

There may be som detent positions on the valve to allow the cylinder ram to freely float in and out (if forced to move).

 

[TheOldHokie]

Hello, I recently plumbed my 3 spool valve to the rear auxiliary block on my B2910 and I've got something wrong. The cylinders extend but I have to bump the control lever to make them retract. I'm sure I've plumbed something backwards. The spool valve has 3 ports labeled "In", "Out" and "PB".
Currently (I think), I have "In" connected to the top port of the Aux Block, "PB" to the bottom port of the Aux Block and "Out" is teed to the tank return located mid tractor where it's shared by the loader tank return.
Any and all help is appreciated.

That is correct. Since you "think" thats what you did I suggest you recheck your connections.

Dan

 

[B leever]

Thanks all, The PB and IN lines were reversed, tank was correct. The tractor is much happier. Now I'm just wondering if I did any damage to the hydraulic system but it works fine and doesn't;t leak so I guess time will tell.

 

[TheOldHokie]

Thanks all, The PB and IN lines were reversed, tank was correct. The tractor is much happier. Now I'm just wondering if I did any damage to the hydraulic system but it works fine and doesn't;t leak so I guess time will tell.

I thought that might be the case. You are not the first to do that and the only thing even remotely at risk for damage is the valve itself. The valve might have compromised seals but nothing major.

Dan