I recently purchased a used BT1100 to go on my L48 which has never had a backhoe on it. The seller disclosed that the swing function didn't work but no other info. I got it anyways with the BT1100 being basically unobtainable and it was still a great price. Brought it home on a trailer, and it sat on the ground for a week or so while I waited on the rest of my tractor side plumbing to come in so it could be connected. In the back of my mind, I sort of hoped that the issue would lie inside the previous owner's tractor, or at least be something super simple. Well, it's been anything but that. I need a hydraulic guru to step in and tell me something new, because I'm out of ideas. A new complete valve assembly is nearly $3,400 and I'm not looking to go there unless absolutely necessary. These are some fancy proprietary Husco 5000 series valves, looks like only available from Kubota and half the parts are discontinued.
Upon connecting to my tractor, as stated all the functions worked except for swing. I did feel like the rest of the hoe ran kind of slow/weak, but I'm accustomed to mini excavators so I don't really know what it's supposed to feel like on the L48. When you hit the swing function, the system simply dead heads and goes to relief. The swing cylinders do not move other than a slight attempt to move as you return the spool to neutral. If you cycle the spool about 10 times, you can get it to move a couple inches. Also, while cycling this spool, the other functions seem to lose some pressure momentarily. (I.E. when I cycle the swing spool, during that same moment that it moves an inch on return to neutral, the boom will also fall a little bit). Again, rest of the hoe works as intended. Maybe a little weak but I figure I probably just need to adjust the relief valve later. For those not familiar, the swing function on this backhoe is fed by a separate hydraulic pump than everything else. Just upstream of the swing spool valve is a "mid inlet" section where this pump feeds in.
First off, yes, the swing lock pin is removed.
- I tee'd in a gauge on the swing lines coming off the spool valve. No matter which way you operate the spool, both of the hoses instantly charge to 2500psi. It acts like there is no return.
- I have thoroughly checked all of the swing circuit plumbing, making sure no hoses are hooked up wrong. Everything matches the Kubota diagrams exactly. All hoses flow freely and have no damage.
- I have disassembled the swing cylinders, there is no damage to the bore, piston is intact, the seals even looked good. I got them replaced anyways.
- I have had the valve stack off the hoe, disassembled and checked that all the parts were there NUMEROUS times. I have even tried swapping the spool valves around to rule out a bad valve. The old swing valve works fine in a different position (I.E. boom, dipper), valves that worked before no longer work when placed in the swing position.
- I have swapped around the port relief valves in case one of those was bad, no change.
- I have tried connecting the swing valve to different cylinders just to make sure, no change.
- I removed every single spool and compared them, even tried swapping some around just in case the wrong one was in there, nope.
- From everything that is visible, everything inside the valve assembly looks exactly how it should. No trash, no corrosion, no visible cracks, no scoring, nothing. You can look straight through the return path and there's nothing in the way.
At this point, it seems to be a problem in one of the valve castings but I can't find it. What would cause this to happen?? I can't think of any logical explanation. You can shine a flashlight down the return path in the valve assembly and its wide open, absolutely no reason fluid should not be able to return down the path unless some part is missing or someone has reassembled it the wrong way. I've spent hours starting at Kubota diagrams and the WSM trying to find anything missing or put together wrong, but everything seems to match...
I've actually blown the outlet seal on the tractor's swing pump just from messing with this thing. The shut off plug on the bottom of the mid inlet casting is leaking like crazy when you operate the swing too... I'm just hoping someone has faced this and knows something I don't, because this thing has had my head spinning for weeks now. No hydraulic shop in my area has equipment to bench test the valve. I'm essentially on my own with this one.
Any ideas would be greatly appreciated!
Upon connecting to my tractor, as stated all the functions worked except for swing. I did feel like the rest of the hoe ran kind of slow/weak, but I'm accustomed to mini excavators so I don't really know what it's supposed to feel like on the L48. When you hit the swing function, the system simply dead heads and goes to relief. The swing cylinders do not move other than a slight attempt to move as you return the spool to neutral. If you cycle the spool about 10 times, you can get it to move a couple inches. Also, while cycling this spool, the other functions seem to lose some pressure momentarily. (I.E. when I cycle the swing spool, during that same moment that it moves an inch on return to neutral, the boom will also fall a little bit). Again, rest of the hoe works as intended. Maybe a little weak but I figure I probably just need to adjust the relief valve later. For those not familiar, the swing function on this backhoe is fed by a separate hydraulic pump than everything else. Just upstream of the swing spool valve is a "mid inlet" section where this pump feeds in.
First off, yes, the swing lock pin is removed.
- I tee'd in a gauge on the swing lines coming off the spool valve. No matter which way you operate the spool, both of the hoses instantly charge to 2500psi. It acts like there is no return.
- I have thoroughly checked all of the swing circuit plumbing, making sure no hoses are hooked up wrong. Everything matches the Kubota diagrams exactly. All hoses flow freely and have no damage.
- I have disassembled the swing cylinders, there is no damage to the bore, piston is intact, the seals even looked good. I got them replaced anyways.
- I have had the valve stack off the hoe, disassembled and checked that all the parts were there NUMEROUS times. I have even tried swapping the spool valves around to rule out a bad valve. The old swing valve works fine in a different position (I.E. boom, dipper), valves that worked before no longer work when placed in the swing position.
- I have swapped around the port relief valves in case one of those was bad, no change.
- I have tried connecting the swing valve to different cylinders just to make sure, no change.
- I removed every single spool and compared them, even tried swapping some around just in case the wrong one was in there, nope.
- From everything that is visible, everything inside the valve assembly looks exactly how it should. No trash, no corrosion, no visible cracks, no scoring, nothing. You can look straight through the return path and there's nothing in the way.
At this point, it seems to be a problem in one of the valve castings but I can't find it. What would cause this to happen?? I can't think of any logical explanation. You can shine a flashlight down the return path in the valve assembly and its wide open, absolutely no reason fluid should not be able to return down the path unless some part is missing or someone has reassembled it the wrong way. I've spent hours starting at Kubota diagrams and the WSM trying to find anything missing or put together wrong, but everything seems to match...
I've actually blown the outlet seal on the tractor's swing pump just from messing with this thing. The shut off plug on the bottom of the mid inlet casting is leaking like crazy when you operate the swing too... I'm just hoping someone has faced this and knows something I don't, because this thing has had my head spinning for weeks now. No hydraulic shop in my area has equipment to bench test the valve. I'm essentially on my own with this one.
Any ideas would be greatly appreciated!
