L48TLB

[arborcare]

Please advise your comments...
My L48tlb with 235 hrs. 10 months old has had hydraulic leak down problems. If loader is about 6" off ground, it will drop to ground in about 20minutes. Backhoe will drop even faster. Just the other day, we broke for lunch and came back to find backhoe resting on the ground. Dealer replaced all seals in rams, but this did not seem to fix. Dealer advised some leakdown is normal. Also, dealer advised joystick valve bodies are " machine fit" spools. No seals. Please advise your comments. /forums/images/graemlins/confused.gif /forums/images/graemlins/confused.gif

 

[Henro]

Hopefully some L48 owners will give you some specific answers.

Leakdown is normal from everything I have read here and elsewhere. My impression is that generally it is caused more frequently by leakage within the control valve than by leakage past cylinder seals. But this could just be my impression...

I would ask the dealer what the Kubota spec for leakdown is. I recall reading something somewhere that had a value given, but sure can't remember where or how much.

On my B2910, the loader will hold position for a long time. I never checked how long, but if I forget to lower it to the ground and I leave it in the air over night, it will still be off the ground the next morning. But the backhoe will drop to the ground, as will the backhoe stabilizers over time.

Six inches in 20 minutes sounds like a lot to me (18" in an hour) but I don't really know. Hopefully some L48 owners will chime in. By the way, I have 330 hours on my tractor, which is almost 2 years old, a high percentage of which is loader hours...

 

[_RaT_]

Most of the time leak down is never an issue unless it leaks down so fast that while setting heavy objects with either the hoe or the loader you can not maintain position of the object while it's being set. I see it frequently on old industrial hoes when we would set concrete boxes. The control valves have to have some clearance around them in order to make them workable and not to stiff. It most likely is in the valves. My L48 did not have an appreciable leak down, at least, not to the extent that I ever took notice.

 

[rbargeron]

On commercial machines they use pilot-operated check valves on the cylinders so they stay put for hours or even days. But the typical compact TLB buyer doesn't want to pay $65k for a 50 hp machine, so they cut corners to keep the price in line.

It sounds like this valve has a body bored at the high end of the tolerance, and a spool that's at the low end - so it has some leakage with the valve centered. There's probably a published leak-down spec somewhere - maybe this rig is outside it ?

 

[uhmgawa]

</font><font color="blue" class="small">( Dealer replaced all seals in rams, but this did not seem to fix. Dealer advised some leakdown is normal. Also, dealer advised joystick valve bodies are " machine fit" spools. No seals. )</font>

It is likely the spool valves which are causing the drift. The spools are
ground for a close fit in the valve body and allow a slight amount of
oil to leak across the ports.

The HUSCO valves OEM'ed by Kubota are notorious for hydraulic
drift. However such drift is typically an annoyance rather than an
operational problem. If this is not the case for you and the valves
are worn beyond specification I'd have the dealer replace both loader
and BH valves as the machine is still under the 12 month blanket
warranty.

When I took issue with the drift I saw in my L48 after only ~30hours
of operation the delaer told me my case was minor compared to the
average [ie: live with it.]

The permanent repair would be to toss the HUSCO valves and replace
them with valves from a more mainstream manufacturer. Prince or
Gresen would be my choice.

 

[gray]

Hi.

I have an L48 that also has leak down but not as bad as you mention. I think the others have it about right, it is the valve bodies that cause it. When I take my Back hoe off for a while, it holds just where I set it. This seams to me to indicate that the fluid has no place to go even if passing the valves so the cylinders stay put. If it were leak past the cylinders this would likely not happen.

My loader leaks down about 6 inches per 2 hours and the BH boom drops to the ground in aobut 4 days. I have gotten used to using the boom lock when it is on the trailer. I just wish it had a hinged easy to use lock. Not the pin you have to place in or remove- lazy?

Good luck.

BTW- I really like my L48.

 

[rbargeron]

Leak-down of my Bradco is very little. But when my kids were small, I got into the habit of always leaving the FEL, backhoe, etc. resting on the ground, all pressure fully relieved, tractor off, etc. so if kids climbed up and played with the levers nothing would move. So leak-down is only rarely noticed in my case. The kids are grown, but leaving the tractor in a fully "relaxed" state is still a good habit.

 

[gray]

While on one of my unplanned road trips today I thought of a possible fix for the leak down?

The main boom cylinder and the two main loader lift cylinders are the only ones that really cause much issue with leak down. I believe Surplus Supply and other hydraulic suppliers may have check valves that if put in line on these three cylinders that may fix this issue?

Would this work?

 

[L3710GV]

Also the better valves have "load checks" built in to slow the leakdown, when the tractor is running.

If the bucket or hoe boom drops with tractor running-then you have a problem /forums/images/graemlins/frown.gif