LK3054xs Backhoe KB2376 valve body problem looking for thoughts

[JoelD]

Moving snow last night. After about 20 minutes or so my loader loses power and will not lift. I get off machine thinking my pump gave up the ghost. Then looked for leaks. Then tried the backhoe. Realized the dipper stick, joystick was stuck forward wedged up under the backhoe seat. I pushed it towards back of machine to lower the dipper stick. The lever was tough to move, after a bit of back and forth it freed up and dipper worked as designed. Loader again worked perfect. After another few minutes the dipper stick joystick was again moving forward and trying to lift the dipper with loader losing power as oil was flowing to dipper stick piston, which would not lift any more and oil was diverting. Again joystick was tough to push to back of machine, after a bit of moving around it freed up.

All along the dipper stick and hoe functioned fine and no oil leaks.

Obviously something is up with the valve assembly. Trying to figure out why it would behaive the way it is. I've replaced most of the o-rings in the valve body.

I'll pull appart when it gets warmer. in the meantime I'll likely remove the hoe and put on my snowblower, was hoping to avoid as snow fall has been light this year.

Any and all thoughts appreciated.

Why would the dipper stick valve work its self to lift position and and stick there and be tough to release then after release be back to normal operation and then work its self back to on again?
Thanks,
Joel

 

[VictorW]

I have a KB2375 on my CK30hst. The only thing that centers the valve, or actually centers the spool in the valve block, is a spring attached to the bottom of the spool that protrudes beyond the bottom of the valve block inside the approximately 1 1/2 " x 1" cup which is attached to the bottom of the valve block. The spring either compresses against the valve block when the spool is lifted or is compressed against the cup when the spool is pushed down causing the spool to want to return to a neutral position. This design is very similar to the springs on the ends of the spools in the loader valve block. Members, including myself, have had moisture enter the cup of the loader valve making it stick or hard to move. I would remove the cup from the bottom of the respective valve block and check for corrosion, possibly a broken spring, or a broken screw at the end of the spool that secures the spring in position.

 

[Patches]

Joel; why not switch your power beyond line back to the tank and disable the hoe till you have time to play with it. Seems easier than dropping the hoe and having to go through the hassle of re-attaching the hoe later. This assuming you still have the boom locking pin?

 

[JoelD]

Thanks patches and victor

Good point patches!! Will do tonight

Victor, I was thinking something similar with regards to moisture. I re-o-ringed a few of the valves in the valve body this fall as I had a couple of leaks and I did find some moisture in a couple of the cups as I was doing the stabilizer valves

I will drop this cup and see what I find

Weird that the valve would work its self to the dipper stick lift up position on its own.

Problem in cup would explain why I did not see leak as u expected to see leak with the tough to move joy stick


Joel

 

[JoelD]

OK, so I pulled apart the backhoe valve body, for what seems like the 100th time.
I noticed before I removed from the tractor that I had oil coming out of the dipper stick control valve lower cups.
I pulled the cups off the bottom of the dipper stick control valve. Nothing looked wrong, I replaced the black o-ring just to be safe ($8 a pop for an o-ring, nutty, there's got to be an equivalent out there somewhere). I put back together and then installed back into tractor.
Still same problem, after a couple of minutes of the tractor running the dipper stick control valve starts to move itself into the up position and the hydraulics are under load.
I don't understand why this would happen? Are there any seals within the valve body or are there only the 0-rings and dust seals at either end and internally is up to close tolerances between the double acting spool and the valve body?
I'm stumped?
Thanks,
Joel

 

[VictorW]

Other than those black rubber o-rings and white nylon backup washers at each end of the spool, no other seals within the block. As you said, just very close tolerances between the bore of the block and the spool. The problem I had when new was if I would just start to move the level ever so slightly to lower a stab a little more, it would let off pressure allowing the stab to move up. There was a problem/warpage in the chambers of the cast valve block that didn't allow the spool grooves to line up properly with valve chambers. New block with the old spool and related parts and all was fine. Yours was working ok from the start so something must have warn or is sticking to make it fail. I would think the spool and valve block are good. Another thing that I can think of is the valve blocks each have check valves. I assumed these check valves just held the fluid pressure/cylinder rod position when the spool is centered. Lastly is port relief valves and I'm not really sure how they work or what they actually do. I can't think of anything else because that's all the parts that are there in this simple design of a valve. Maybe give Bob, parts person, a call at Michigan Iron and Equipment. He's very knowledgeable. This should be a link to your valve block assy. Error

 

[JoelD]

Thanks I will pull the spool completely apart and see what I find

Joel

 

[JoelD]

As there are only seals at either end of spool I am wondering if something may be stuck within the spool? I will remove spool and see what I find
Curious problem
Joel

 

[VictorW]

There is something redirecting fluid pressure and forcing the spool to move. The valve block is cast and has several chambers. You'll see the chamber dividers when you look into the valve block with the spool removed. The spool is just a round shaft with grooves cut into it at various designed positions along the shaft that relate to the chambers in the block. As the spool goes up and down, those grooves allow fluid to be redirected to the various chambers which controls which of the two attached hoses gets pressure and which one acts as a return. Otherwise, when the spool is centered, it's an open center valve allowing fluid to flow through the valve and not to the hoses. Maybe it's one of the two relief valves on the block that is stuck and putting fluid pressure on the spool. A small piece of dirt or maybe a piece from a damaged o-ring is clogging it up. You mentioned fluid leaking out of the dipper stick control valve lower cup. There should be none and that cup isn't made to hold 2000psi pressure. Also, the o-ring is for seepage not full pressure. For some reason pressure is building in that valve block that shouldn't be which maybe a relief valve is stuck. Sorry I don't have the answer for you. Never had that problem but I think after disassembling that valve block and a good cleaning, you'll find the problem. One other way to possibly diagnose the relief valves is to change them from the dipper block, one at a time, with another good block and see if the problem moves to that valve block.

 

[JoelD]

Excellent advice I will go through the relief valves.

Over the last couple of months I've replaced all the o-rings due to leaks

Either they've all ages about the same rate or there is something else like relieve valves

I'll pull assembly and go through the relief valves

Thanks
Joel