Backhoe Swing Issues

avc8130 · Dec 20, 2014

I know it has been talked about before, but I can't find a real reasoning or resolution to the Kubota backhoe swing issues.

I was using my L45 this morning to move and cut logs for firewood. Suddenly the backhoe swing stopped working in the "left" direction. Right worked fine but there was no hard stop when I let off the control.

I know from the past and searching on this site that to "fix" this you have to jack one stabilizer up, crank up the rpms and continuously cycle the hoe swing allowing gravity to swing it in the failed direction.

Sure enough, after doing that about 2 dozen times the left swing "works" again.

I'm still scratching my head.

WHY DOES THIS HAPPEN in the first place? Can it be "fixed" permanently?

ac

Kanook · Dec 20, 2014

I've had similar problem with a 3rd party hoe (Wallenstein) and same solution. Am curious as to what caused this problem ..I attributed my issue to air in the line...but was just guessing.

sandyc · Dec 21, 2014

Just a guess......air in the lines.

JOHNTHOMAS · Dec 21, 2014

If you ever have one that won't start working again then take the cover off the controls for the BH. There are 4 rods that connect to the two operating handles. There are two tiny screws that come up from the bottom side into the attached nuts and one of these fell out on my B2620 BH. I found the tiny bolt the first time but not the second time. Cost me about $4 for one from Kubota. Really hard to get into the spot. Should have taken a pic but tractor now gone. The two bolts are holding a small rectangle shaped plate on that keeps the whole thing together/working. If you notice the control getting a bit sloppy and not moving precisely then stop and get that cover off and feel those rods and make sure they move but don't have slack in them and locate the two bolts I'm talking about and make sure they are tight.

Tailrotor · Dec 21, 2014

It's sounds to me that the spool valve is sticking which is what John Thomas is taking about under the cover.

When you press the joy stick it pushes in on the valve and let's the fulid flow when you release the joy stick the valve should return and stop the flow of fulid and seat. If the valve does not seat you will have some bypass which will cause the boom to continue to swing and not the hard stop we are use to.

On my L45 I had a issue with this also I removed the cover and found the screws that hold the valve bodies on had back out and would jam the spool against the housing body and it would still flow and have swing.

I tighten all the screws on the valve body and have not had a problem with it since.

So think of this way it's a square cap with a hole in the middle that has 4 little screws that hold it down and there is a plunger that sticks up from the middle hole of the square cap and some of the screws that hold it down come loose on one side now that plunger is no longer center in the square housing and drags the side allowing the fulid to continue to flow and still have boom swing.

When I fixed mine there were serveral screws lose on all the valve bodies top and bottom after fixing it I haven't had any issues and I have 200 hrs on mine and it did it when mine was brand new my dealer is the one that told me what to look for he said this is a common problem on the early units.

Don't know if this is what is wrong with yours just wanted to post maybe it will help

Merry Christmas to all.

Stonehaller · Dec 21, 2014

Make sure the directional lever for the swing pump is fully in the correct position. I presume the L45 has similar levers to my L39. There are two levers on the back of the tractor. They are pulled out for operation without the backhoe and pushed in for operation with the backhoe. The one lever dumps all oil for the swing pump to tank and if it was partially engaged you would not get full pressure or flow for backhoe swing. The other lever routes the main pump oil to the three point lift.

avc8130 · Dec 23, 2014

sandyc said:
Just a guess......air in the lines.

Where would the machine keep getting air from? And especially only in the swing? This never happens to any of the other circuits.

ac

avc8130 · Dec 23, 2014

Stonehaller said:
Make sure the directional lever for the swing pump is fully in the correct position. I presume the L45 has similar levers to my L39. There are two levers on the back of the tractor. They are pulled out for operation without the backhoe and pushed in for operation with the backhoe. The one lever dumps all oil for the swing pump to tank and if it was partially engaged you would not get full pressure or flow for backhoe swing. The other lever routes the main pump oil to the three point lift.

Yeah, I've checked that. My L39 taught me that lesson too.

ac

avc8130 · Dec 23, 2014

Tailrotor said:
It's sounds to me that the spool valve is sticking which is what John Thomas is taking about under the cover.

When you press the joy stick it pushes in on the valve and let's the fulid flow when you release the joy stick the valve should return and stop the flow of fulid and seat. If the valve does not seat you will have some bypass which will cause the boom to continue to swing and not the hard stop we are use to.

On my L45 I had a issue with this also I removed the cover and found the screws that hold the valve bodies on had back out and would jam the spool against the housing body and it would still flow and have swing.

I tighten all the screws on the valve body and have not had a problem with it since.

So think of this way it's a square cap with a hole in the middle that has 4 little screws that hold it down and there is a plunger that sticks up from the middle hole of the square cap and some of the screws that hold it down come loose on one side now that plunger is no longer center in the square housing and drags the side allowing the fulid to continue to flow and still have boom swing.

When I fixed mine there were serveral screws lose on all the valve bodies top and bottom after fixing it I haven't had any issues and I have 200 hrs on mine and it did it when mine was brand new my dealer is the one that told me what to look for he said this is a common problem on the early units.

Don't know if this is what is wrong with yours just wanted to post maybe it will help

Merry Christmas to all.

I'm going to have to check into this. This has happened a few times on this machine and my L39.

Every time I think it was caused by working the swing up against the pressure relief. One time on the L39 I tried to swing the hoe but forgot to remove the swing travel pin. This latest time on the L45 I was trying to pull logs from a pile with swing.

So it's like the swing circuit gets stuck in "relief". What amazes me is if you search TBN you find this is common.

ac

Stonehaller · Dec 23, 2014

Another possibility is the port relief valves in the swing circuit. These are set a few hundred PSI higher than the pump relief so it takes an external load or the inertia from swinging fast and stopping to open the relief. If the relief poppet for one side got stuck open or was leaking, then oil pressure would be dumped to tank and it would not have much power in that direction but it would have power in the other direction. There are also anti-cavitation checks on each port, that if stuck open would do the same thing. The check and relief is part of the same assembly that is screwed into the valve and it may be worth pulling them off for inspection and cleaning.