kubota bh77 dipperstick cylinder problem

[DB Pilot]

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]

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]

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

 

[DB Pilot]

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]

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]

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]

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]

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]

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]

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.

 

[rScotty]

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.

Here's part of message #5 that might be worth thinking about or looking up some old threads.

"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."

The subject comes up at least once a year and nobody has figured it out yet. The difference, is that in all those thread it eventually started working again - except one case that had a bad cylinder. The rest are still a mystery. Mine hasn't done it again in the last 5 years or so. In all of those we could move the cylinder by hand or gravity but only power in one direction.

 

[DB Pilot]

okay rScotty, The mechanic down at the shop wants to re-look at the cylinder. :confused3: but assured me they would get it working again. :laughing:

 

[ProjectKing]

okay rScotty, The mechanic down at the shop wants to re-look at the cylinder. :confused3: but assured me they would get it working again. :laughing:

Will be interesting to hear what they find out.

 

[rScotty]

okay rScotty, The mechanic down at the shop wants to re-look at the cylinder. :confused3: but assured me they would get it working again. :laughing:

That sounds good. If he is that confident then I'm guessing their shop has a hydraulic flow & pressure meter. That's the hydraulic equivalent to a electrical Volt/ohm/meter, but less common.

None of the shops that dealt with the mysterious TLB hydraulic problem in messge #5 had a flow meter - which is a shame because using one will generally pinpoint the problem real quick. Otherwise there's a lot of guesswork.

We could do a whole thread on what a good dealership tractor shop should have in the way of tools and training.

Although IMHO, there's still a place for the self-taught savant in his cluttered one-man shop....but they are going extinct around here. If you find one of those you have a gem.
rScotty

 

[nbryan]

Just in case this helps anything, after seeing this, yet another thread about bh77 glitchy behaviour. My BH77 does sometimes lose force with boom and dipper both extended away from the tractor, with down or lift force weak or gone.
Just checked again the action where the valve levers connect to the BH valve body, with the rubber boots lifted off.
I tried moving the levers through a complete range. The levers hit the metal frame AT 3 POSITIONS!
And there's even more interference when the rubber boots are clipped into place.
Moving the dipper/bucket lever all the way forward even hits the guard rail.
My next task is to remove the top plate that the levers pass through and run bh without that interference.
The design of the BH control tower has the levers way off center of the openings. There's lots of room when moving the levers toward the tractor or center.
I may try shimming under the lever mounting plate to help tilt it a bit away from the obstructions.
It should help SOMETHING to allow the valves full range of motion!

 

[nbryan]

The 3 places the lever motion hits the frame.

 

[DB Pilot]

Got the call today that BH77 was repaired and working great. Thirty minutes later I was at the shop. :thumbsup: They fired up the tractor and guess what, same problem. :shocked: I was told they cleaned up the valve area and I don't remember the rest but now we are into replacing some parts. :confused3:

 

[nbryan]

Do your levers hit the frame tube or tower top cover?

 

[rScotty]

Got the call today that BH77 was repaired and working great. Thirty minutes later I was at the shop. :thumbsup: They fired up the tractor and guess what, same problem. :shocked: I was told they cleaned up the valve area and I don't remember the rest but now we are into replacing some parts. :confused3:

Something doesn't sound right here. What is "cleaning up the valve area" mean?

Mechanics that do hydraulic repair have a pressure & flow measuring tool. It's generically called a "flow stand" or flowmeter.....that's the basic tool required for the hydraulic diagnosis. Using adapters, the flowmeter gets plugged into the hydraulic circuit in various places so that pressure and flow can be measured as the control valve is worked. A hydraulic flow stand is to hydraulic repair what a VOM is to electrical work. Otherwise a mechanic is just doing guessing and part replacing - some are pretty good at that kind of diagnosis, but it's a gamble on your dime.

Ask him to go over with you what pressure and flow readings he is getting at various points and what he thinks they mean. Take some notes and maybe we can help here, too. There's a lot of experience on TBN.
rScotty

 

[rScotty]

The 3 places the lever motion hits the frame.View attachment 659117View attachment 659118View attachment 659119

That's just crazy.