Backhoe valve body leak, repair, now real stiff controls

[Duckdogs]

Kioti CK30HST with the KB2375 backhoe. Nimco 1S-5709 valve body Owned since new, 2005.

I've had a small leak for several years that turned into a steady drip drip drip, almost a stream. Removed the valve body & took it to a hydraulic shop for a rebuild. Reinstalled and immediately noticed the controls were a little stiff. The thing failed after 30 minutes & dumped about 2 gallons of fluid on the ground. Back to the repair shop. Was told an O ring blew out and the stiffness was because all the seals were new, will loosen up with use. Reinstalled. Wow, now the controls are so stiff it's impossible to operate. I have to strong arm the joy sticks and they don't seem to want to return to center. I have to physically move them back to the center position. I'm afraid I might actually bend one of the sticks. It just can't be right.

Does anybody have any insight as to the problem? Is there any adjustment to be made? I don't have supreme confidence in the repair shop.

 

[oldnslo]

Is this valve assembly held together with tie rod bolts? If yes possibly tightened to tight causing the spools to bind. No clue on what torque spec should be though.

 

[Duckdogs]

oldnslo,

Hard to tell since it's reinstalled but it appears to be held together with tie rod bolts. I can see the ends of 3 bolts on the right ride and I can see where the top one passes through the middle two (stabilizer) valves. Definitely not a bolt however as it doesn't pass clear through to the left side. Suppose it could be a stud. The other two on the right that I can see are definitely the nut end, can't see the nuts, only tip end of the bolt/stud.

Before I take it back out, I'll try to find the torque spec. If I knew the grade of the bolt/stud I could prob look it up based on the diameter.

Thanks for the tip.

 

[oldnslo]

Duck
I would not use the stud or bolt diameter for torque spec. I have seen some smaller valves with 8 mm tie rods that only had 17 Nm torque (12.5 ft-lbs). Over tighten and these spools would bind from body distortion.

if you can’t find spec on Nimco possibly try similar size valve from Prince Hydraulic or Brand Hydraulic as a point of reference. I think they show assembly torque values on their websites.

Good luck

 

[true temper]

Your valve is junk they didn’t know what they were doing and killed it. Time for a new valve.

 

[MH49]

Do the spools move freely when the tractor is off? It sounds to me like your tank is not hooked up correctly or there is some kind of restriction in the tank line. This would also cause the valve to feel stiff and seals to blow.

 

[Duckdogs]

Update on this....

(The spools were binding no matter if the tractor was on or off or if the valve body was on the hoe or on the workbench.)

Took it back to the repair shop. The O ring that "blew" was between one of the spool valves and the inlet section. The repair guy was unable to work the valve by hand. (No wonder, I only able to move the valve with great effort with the leverage of the stick attached.) So I ask to look at one of the spools. After removing the fasteners he is unable to push the valve out. Small hammer, tap tap tap, no help, not coming out. He decides the bolts holding the sections together are too tight. Uses cordless impact driver to loosen. Now it pushes right out, appears undamaged and replaced it operates smoothly by hand, (no stick atttached) I probably should have insisted on inspecting all the spools but didn't. Hope they are ok. Not sure what to look for other than the obvious, burrs, deformities, etc. He does not know what the torque spec should be. Neither do I. Hate to just snug it up by feel & find out not tight enough after install.

Oldnslo suggested I look at a similar size valve from Prince or Brand. I'm not sure which of their products are a match but the torque specs range from 7 ft/lb for a Brand product to 12.5 and 30-32 ft/lb for Prince.

I have called the manufacturer. They won't return my call. I ordered the factory manual for the hoe but don't have it yet.

Does anybody here know how tight the bolts holding the sections together should be? Nimco 1S-5709.
Because that's definitely the problem.

 

[oldnslo]

Duck
If torque spec is not known I would suggest looking at the stud size and then torque them to half that stud size rated spec. Do the spools still move smoothly? If yes torque another 2 ft-lbs, still move free, another 2. When you start feeling drag you have found max. I would then back them off and retorque to value slightly lower than when spools started to bind. Not exact but better than what you had. Hopefully the tie rods or studs have not been compromised by over tightening

 

[true temper]

I was wrong, I figured that the spools were gualded and would never move smoothly again.

 

[wdchyd]

Common issue from a fresh repair, if any rust (very common) or grit between the sections will warp the valve section during torque up. The spools are machined to super tight clearances (less than .0005” sometimes) and one small speck of sand can bind up the valve. We use
a new flat stone dedicated to barely lap the section flat surfaces before a thorough rinsing in the solvent tank. I’ve seen others use sanders and disc grinders completely ruin the critical mating surfaces from butcher repairs several times.
Cleanliness is critical but gets overlooked by others real easy.