kubota bh77 dipperstick cylinder problem

DB Pilot · Jun 3, 2020

Anyone have this problem with their BH77 backhoe? All has been working well for 5 years. For some reason the Hydraulic cylinder for extending the arm has stopped working. All other cylinders are working bucket curl, raise and lower boom, stabilizers and left right are all working properly except the dipper stick cylinder. I used it yesterday morning and it worked well. That afternoon I could not extend the bucket arm but after awhile all worked again. Today I cannot get the cylinder to extend the bucket arm. I can push the bucket out with my foot and it will come back in with the control but only a foot or so. My dealer is recommending a cylinder rebuild but I am not sure. The controls will bring the bucket in for transport. Anyone ever have this problem? :confused3:

ProjectKing · Jun 3, 2020

Need to take the cover off the linkage and make sure the levers are actuating the valves properly. The linkages can become loose, etc and cause issues.

RickB · Jun 3, 2020

The piston may have disconnected from the rod (inside the cylinder). Yes, I have seen that.

DB Pilot · Jun 4, 2020

Thanks to both ProjectKing and RickB. Both answers seem very likely. I will check out linkage today first. When I push the control lever to extend the boom the hydraulic hose surges. Which might mean looking inside the cylinder.

I'll let you know what I find and hopefully some pictures. :thumbsup:

rScotty · Jun 4, 2020

DB Pilot said:
Thanks to both ProjectKing and RickB. Both answers seem very likely. I will check out linkage today first. When I push the control lever to extend the boom the hydraulic hose surges. Which might mean looking inside the cylinder. I'll let you know what I find and hopefully some pictures. :thumbsup:

That's a good observation about the hydraulic hose surging. I sometimes disconnect a hydraulic line and insert a short "T" made up with a $20 5000 psi pressure gauge on it. The whole "T" tool cost about $50 to make with adapters.

I'll be interested in what you find. It sounds kind of similar to threads you may have seen here about Kubota TLBs that mysteriously lose and then regain their BH swing function. But you could move it by hand. That's been going on for ten years or more, and by now a dozen or more owners have reported it happening to them..... and we still haven't figured out why it happens.

There was one recall on a Kubota BH cylinder I heard about a decade ago. But that was the boom cylinder not the dipperstick, and it moved both directions but had a problem in that it would not contract enough to engage the boom lock.

My experience is that cylinders are pretty reliable. For the occasional problem I've had very good luck taking cylinders to a local hydraulic shop for rebuild. Cylinders taken to the dealer usually end up at the hydraulic shop anyway.

rScotty

DB Pilot · Jun 4, 2020

Looks like we are all on the same page here.

I checked the linkage this morning and all seems correctly connected and moving. I now have the cylinder off the BH. :thumbsup: Right now I believe the nut on the hydraulic piston has come off.

Since the cylinder arm contracts in order for the boom to extend (it can't pull) but can push the piston out to bring the bucket back in (which it does). My local welding shop has rebuilt things for me or will know exactly where to take it. I will definitely let you know what happens.

crazyal · Jun 4, 2020

I had the nut come off the same cylinder on my case BH. If you grabbed the bucket you could pull it and the dipper would swing easily. Once you remove the gland nut it's not that hard to remove the piston. If you don't have the tools to remove the gland nut then anybody who rebuilds cylinders can do it.

ProjectKing · Jun 4, 2020

DB Pilot said:
Looks like we are all on the same page here. I checked the linkage this morning and all seems correctly connected and moving. I now have the cylinder off the BH. :thumbsup: Right now I believe the nut on the hydraulic piston has come off. Since the cylinder arm contracts in order for the boom to extend (it can't pull) but can push the piston out to bring the bucket back in (which it does). My local welding shop has rebuilt things for me or will know exactly where to take it. I will definitely let you know what happens.

Wow. Thank you for sharing. I agree a cylinder shop should be able to repair. While they have it torn apart they should put in new seals too.

How many hours are on this backhoe?

DB Pilot · Jun 4, 2020

Hours on tractor read 700+. But the backhoe I would guess about 100- hrs. It is about 6 years old and I would not want to be without it. Cylinder is in the shop right now and hopefully I will know in a day or two if it is the problem.

DB Pilot · Jun 8, 2020

Well we found out it is not the cylinder. Air pressure works that back and forth just fine. The linkage is tight and seems to be working the valves correctly. My Tractor and backhoe are now in the shop as I am over my head now that we are talking valves or a blockage of some sort.

One word of obvious advice "never take a BH off the tractor if it isn't working properly". :2cents: I did so I could mow with the 3 pt finishing mower. Getting the BH back on without all controls was a one hour operation. :duh: Lesson learned.