Loader I Buggered Up My Loader

[herringchoker]

KubotaB7800, LA402 loader, 830 hours. Fluid was seeping around the rod on both bucket cylinders and one boom cylinder, and the loader leaked down slowly. So I rebuilt those three cylinders using genuine Kubota rebuild kits, reassembled everything and topped up the hydraulic fluid. I have cycled the circuits to bleed air.
Now there is a problem. The bucket works fine but the boom is erratic:

• The boom is extremely slow to raise, except if I curl back or dump the bucket while at the same time raising the boom, the boom raises as normal only after the bucket is fully dumped or fully curled.
• If I try to start raising the boom with the bucket fully dumped or fully curled, the boom is still slow. (The full extension or retracting of the bucket cylinders while the boom is raising seems to be the only way to kick the boom into normal lift.)
• When I first pull back the lever to raise the boom (if the bucket is not on the ground), the boom actually drops first about 2” at the bucket.
• The boom will not lift the front of the tractor.
• If I try to lift the front of the tractor using the bucket, all it does is collapse the boom cylinders.
• There are no obvious external leaks or seeps.

The dipstick shows full fluid. I cracked the line to the pressure end of the rebuilt boom cylinder while the boom was raised and fluid seeped out.
I had detached the loader to make it easier to get at things. After reattaching the loader I re-checked the hydraulic quick connects...they look OK.

I'm confounded more than usual. Everything worked fine before I took things apart. Anyone have any ideas?

 

[ptsg]

Sounds like you either crossed some lines during reassembly or you have crossed the quick disconnects.

You may want to double check that.

 

[LouNY]

most likely crossed someplace.

 

[herringchoker]

most likely crossed someplace.

Thanks, guys. Makes sense so I went out and double checked lines and disconnects. They are all good, they're colour coded so easy to trace. I think I'll sleep on it and maybe take apart the rebuilt boom cylinder to see if I messed up inside that.

 

[greenie]

Interesting.... When you figure it out would you post what the solution was? We had a L3400 and in below freezing weather the bucket wouldn't operate but the boom would. Never did figure that out but I assumed it was in the spool assembly (lever control assembly).

 

[mrmikey]

May sound odd but any chance you could have put the boom seals in backwards?

 

[herringchoker]

May sound odd but any chance you could have put the boom seals in backwards?

I don't think so, but that's where I'm looking next (I have been wrong before!). The piston seals have to seal in both directions...the external seal against the barrel is two pieces, an inner square section rubber ring and a synthetic square section ring on top of it. That synthetic seal is a bugger to install, have to stretch it to get it in place and then carefully compress it into the groove on top of the rubber ring while not twisting it. The piston is sealed against the rod by a tiny rubber o-ring that has to be slid over the threaded end of the rod, so chance for damage there too.
The gland seals have to seal in one direction only so they can be installed backwards. There is no apparent external leak, so I think they are okay.
Anyway, I'm about to dive in and see what's there.
Will keep posting what I find.

 

[herringchoker]

Interesting.... When you figure it out would you post what the solution was? We had a L3400 and in below freezing weather the bucket wouldn't operate but the boom would. Never did figure that out but I assumed it was in the spool assembly (lever control assembly).

Will definitely do.

 

[dodge man]

Did you take the quick connects off and back on just to make sure they are seated. I’ve owned a tractor 14 years and twice I’ve not got them seated. They 100% look ok and won’t pull loose but aren’t on correctly. I’ve actually had things work backwards when this happens.

 

[CH4Ohio]

I don’t think your problem is inside a cylinder.