KB2375 control valve

   / KB2375 control valve #1  


Super Star Member
May 20, 2004
Big Island, HI
LS XR4140H (Mine) BX2380 (wife’s)
After not using my backhoe for the past year, this week I was ready to start a major trenching project. Finally, got the hoe mounted and about the 3rd attempt to scoop some dirt all H broke loose - hydraulic fluid.

Appears that some sort of plastic/nylon piece broke in the Boom portion of the control valve. You can see it at end of red arrow.

Judging from the exploded parts manual, I'm guessing it is item #40 - Guidence. So I have ordered replacement and new O rings.

If any words of wisdom out there, I'd be appreciative. I haven't disassembled anything yet, most likely Sunday.



  • KB2375 BoomV.png
    KB2375 BoomV.png
    515.6 KB · Views: 633
  • KB2375 CV.png
    KB2375 CV.png
    63.9 KB · Views: 905
  • KB2375 CVlist.png
    KB2375 CVlist.png
    25.1 KB · Views: 293
   / KB2375 control valve #2  
That nylon ring is a support for the rubber o-ring seal which apparently cracked and let the seal go and the fluid fly. A few years ago, I had to completely remove the entire valve unit from the bh and then split the six blocks apart to replace one of the center blocks that worked a stabilyzer. My replacement was each individual part to make up the complete block. Not that bad once you see what's all there. You should be able to replace the seals without removing the entire valve unit but you may be a little cramped for room. You'll have to remove the hand control that works those two end valves by removing the two nuts and then the studs from the tops of the spools. Then the top plate held on by those allen head bolts which will give you access to the seals which sit in a counterbore in the valve. By the picture, it appears that rust on the spool was the cause of the seals letting lose. I would remove the spool and clean all the rust off the top. Polish it with some fine, 600 or finer grit, emery cloth or wet sandpaper for vehicle paint sanding works good also. You might be able to clean the top of the spool without removing it, just make sure you keep everything clean. If the spool has larger rust pits in it, you'll probably need a new one because it either won't seal good or will tear up the new seals after some use. To get the spool out, if needed, you will have to take off the 1" x 1 1/2" or so matching cap/cup off the bottom of the valve block to release the spool from the valve block. It's not that complicated and rather a simple design once you see things. Just remember to keep things as clean as possible.
   / KB2375 control valve
  • Thread Starter
Thanks Victor

You always appear to be ahead of me on these things. I remember reading your posts. Thanks for the tutorial.

Rust is a MAJOR here - a hard fact of life. Unfortunately, it seems my Kioti is quite susceptible. Keeping things in the tractor shed may only slow it down a bit as it is still open and lots of air flow kinda like a three sided leanto.

Hoping tomorrow I can get at it. My hope is to remove valve cover and have enough room for my no-so-nimble fingers.

Will post followups.

   / KB2375 control valve #4  
You could try covering the area that rusted with copper anti-sieze to ****** future rust - living near the ocean wreaks havoc on any metal- as you well know. Also for salt environments is a product called Aluma-guard which is great for any type of aluminum, so you could get a bottle of that and spray the entire valve body once reasembled to coat it with a salt resistant film. I know it works excellent on my boat's marine grade aluminum T-top. :thumbsup:
   / KB2375 control valve
  • Thread Starter
Thanks for the suggestions.

Strangely, we really don't see as much of the salt type damage as I've experienced like living on the coast of Maine. Aluminum actually seems to fare rather well. Our culprit seems to be the rain, which is slightly acidic due to our quite active volcano.

One thing I've noticed, especially on my Kioti attachments/impliments is once the paint is scratched, a rust blister is soon to follow. This is especially troublesome in bolt hole areas or where there is movement between pieces. Much discussion with friends, we come to reluctantly accept it as a cost of life. Just the other day, a good friend was telling me how badly his 8 yo Gearmore flail has rusted out.

   / KB2375 control valve #6  
Just an idea but some members use fluid film on their cylinder rods when they lay up their bh. It might be a pita but maybe pull up the boots from the control rods to gain some access and spray the heck out of the top area when the bh sits. When I had to work on my valve blocks, I sprayed the cast steel block unit with a wax type motorcycle chain lube. It just leaves a waxy non-sticky film when dry. So far so good with no rust.
If you had a chance, how did the repair go? Hopefully, you're back to digging.
   / KB2375 control valve
  • Thread Starter
Thanks Victor
Not repaired yet. I did send my pic to Michigan iron and Robert verified I ordered the right parts, but due to back order they won't ship until 5/11.

Don 't know if you know this answer. But I assume the spool if removed from bottom? Any knowledge there?

That spool actually looked clean and smooth except the very top, so I'm guessing the failure was internal and the high pressure blew out the nylon piece.

I am quite disappointed at the degree of rust and corrosion. Thanks for the film idea. I have used spray on corrosion control I found at Home Depot. I've used it on my battery terminals last six months and so far so good. It leaves a greasy, vaselene like coating.

Thanks for all the help. Will post more.

   / KB2375 control valve #8  
The spool is the same diameter its entire length except for the grooves that regulate the fluid flow and it could come out either end. What holds it in place is a spring, washer, and small bolt in it's bottom end which are all contained in the aluminum cup at the bottom of the valve block. This spring is what returns the spool to it's center position. If you wanted to remove the spool, you have to remove the cup. By that point, it's easier to just let it drop through the bottom. If you wanted it to come out the top, you'd have to find a way to hold the spool from turning while you removed the bolt along with the spring. I'd just let it drop down through and reinstall from the bottom. With all the hoses connected, finding room for the hands will be a pita. You might have to remove a few to get some working room.

The spool should have been sitting in its neutral or center position when it became a little rusted. When working the control, the spool is either pulled up through the block a little or pushed farther down into the block. I'd bet the rust was right up to the seal and when you made the spool go farther into the block, it tore up the seal. Wait until you see how small the seals are and you'll see why they need the nylon ring as a back up and wiper ring. It wouldn't take to much to damage them and the 2000+psi hyd fluid would just blow the nylon ring out as you see in your picture.

If there's anything else I can help you with, just post or pm. Unfortunately, I was close and personal with those valves and had all their parts in my hand. :)
   / KB2375 control valve
  • Thread Starter
Thanks again..

At this point I don't think I'll drop the spool until I have the new parts in hand - a gamble I don't find other damage. What I did do was unmount the whole CV, allowing it to tip forward for finger room. It will be interesting to see what shape the innards are. I'm also wondering if I should purge the hydraulic fluid and refill with new. Is it even possible to drain just the BH and refill?

Of course, waiting for the parts is agonizing!!!!!

   / KB2375 control valve #10  
I'd believe all the bh innards are good being covered in hydro oil and only the outside exposed areas are prone to your weather. Otherwise, your tractor itself would also have innard problems. No nice way to drain the bh without disconnecting the hoses and cylinders or you could give it a transfusion. If your tractor hydro oil is good, the bh oil is also being that it's constantly flowing between the two. I think you'll just need to clean the top of the spool, replace the seals, and be back to digging.
Last edited: