Kubota hydraulic problem ?

[Arky217]

I have a Kubota model L4200 with Kubota loader.
I think it's about a 1998 model; I've had it for about 8 years.
It appears to me to have a problem with the bucket tilt being very weak.
It has been like this ever since I had it.

Just now, for example, I unloaded a bundle of 16 pieces of 29ga. roofing metal, 3' wide x 12' long.
According to several charts I looked up, the total weight ranged from 325# to 375#.

The bucket has 3' long forks, and I had the straps attached midway along the length of the forks.
When I lifted the load to clear the side of the truck, I also tilted the forks downward a little to keep
the straps from sliding back on the forks.

Then as I was lowering the load, the forks started to angle downward and I went to tilt the bucked
back to keep the forks level so the straps wouldn't slide off.

Well, the bucket wouldn't tilt back; in fact when I tried to tilt it back, it actually started to tilt down more.
So, needing to lower the load without the straps sliding forward off of the forks, I then managed to
manually slide the straps on the forks all the way to the edge of the bucket.

Surprise, the bucket still wouldn't tilt back but actually still tilted downward more when I tried to tilt it back.

It sure seems like the tilt should be more powerful than that.
The tilt has the same diameter cylinders as the lift.

Even if the bucket won't tilt back with a load on it, shouldn't it remain in the position
that it's in when trying to tilt it back instead of tilting downward more ?

I was thinking about fitting the tilt with larger diameter cylinders, but I'm now thinking
that there must be something wrong with the hydraulics.
Maybe a leaky valve or something that's letting the fluid bleed back ?

Anyone else have this problem on a Kubota bucket tilt ?

 

[workinonit]

One thing I'm not is a hydraulics expert. It could be your cylinders but I doubt it. It sounds to me like you have an issue with a remote leaking inside. I'm sure some of these Orange guys will chime in shortly.

 

[wdchyd]

One of the two piston seals internally in the curl cylinders are worn or blown. Repack them both.

 

[Dave M7040]

If you take the time to do the following test procedure you will identify if you have a cylinder problem and exactly what the problem is.

There are many stories on the forums of owners damaging their loader cylinders using forks.

The loader valve has its own built in relief valve.

Once you have the control lever in the middle or neutral position, the relief valve is no longer in the circuit and able to protect from over loads.

Back dragging with forks is a common way to bust cylinders internally. The long length of the fork is like a pipe on the end of a power bar. The forces are magnified beyond imagination.

A hydraulic system normally operating at 2,200 to 2,700 psi can easily generate 6 to 7,000 psi using forks.

Dave M7040

 

[true temper]

Your problem is a bad lift check in the control valve. It should never fall while trying to lift.

 

[Seven Gables]

I agree 100% with Daves assessment , I like the 3 step test also , very good way to test . My guess is your relief valve is opening when you open your tilt valve. If your piston seals were bad it would slowly drop with tilt valve in neutral. Length of forks are simply applying to much leveridge

 

[4570Man]

I’m guessing your hydraulics are a little weak but the clamp on bucket forks definitely aren’t helping with strength.

 

[RickB]

If the cylinders did not drift with the valve centered in the hold position the cylinders are OK.
A pressure test at your loader valve work port Quick Connect fittings will verify pump and main relief valve health.
Many CUT loader valves do not have load checks, yours either does not have them or one could be faulty.
375# centered as far out from the bucket pins as you describe could easily create more pressure on the rod side of the bucket cylinder circuit than the relief valve could hold when the curl valve was stroked.
In the absence of a load check in the bucket circuit and given an acceptable relief valve pressure your loader reacted properly to an overload condition.
There's an excellent chance that a set of pallet forks connected directly to your loader frame or QA device would have handled the same load just fine.

 

[true temper]

Rick has got right again.

 

[Arky217]

If the cylinders did not drift with the valve centered in the hold position the cylinders are OK.
A pressure test at your loader valve work port Quick Connect fittings will verify pump and main relief valve health.
Many CUT loader valves do not have load checks, yours either does not have them or one could be faulty.
375# centered as far out from the bucket pins as you describe could easily create more pressure on the rod side of the bucket cylinder circuit than the relief valve could hold when the curl valve was stroked.
In the absence of a load check in the bucket circuit and given an acceptable relief valve pressure your loader reacted properly to an overload condition.
There's an excellent chance that a set of pallet forks connected directly to your loader frame or QA device would have handled the same load just fine.

Thank you all for the replies.

First, let me say that I have heard of the problem of back dragging the bucket
and I have never done that nor have I ever put any down pressure on the forks
when they are on the bucket.

Just to make sure I understand what was said, let me mention again that even
when the load (325 to 375 #) was hanging from the front edge of the bucket (not out from the bucket edge on the forks any way at all),
that the curl would hold and not tilt down when I was not touching the control lever,
but if I moved the control lever to curl back the bucket, that is when the bucket tilts down instead of curling back.

In fact when I at first had the load attached at midway on the forks (about 18" from the bucket edge), the bucket would still
hold it own until I tried to curl it back. In other words, it would only tilt down when I was moving the control lever to curl it up.

According to the first sentence in RickB's quote above, that would seem to indicate that the problem is not the cylinders.

Even so, does that mean that the problem could still be in the curl cylinders or not ?

Or does that mean that the problem is elsewhere ?

And when I make the tests in post #4, and if the cylinders pass the tests, what then could the problem be ?

And if it's a messed up valve in the control, is there any way to test for that ?

 

[RickB]

Thank you all for the replies.

First, let me say that I have heard of the problem of back dragging the bucket
and I have never done that nor have I ever put any down pressure on the forks
when they are on the bucket.

Just to make sure I understand what was said, let me mention again that even
when the load (325 to 375 #) was hanging from the front edge of the bucket (not out from the bucket edge on the forks any way at all),
that the curl would hold and not tilt down when I was not touching the control lever,
but if I moved the control lever to curl back the bucket, that is when the bucket tilts down instead of curling back.

In fact when I at first had the load attached at midway on the forks (about 18" from the bucket edge), the bucket would still
hold it own until I tried to curl it back. In other words, it would only tilt down when I was moving the control lever to curl it up.

According to the first sentence in RickB's quote above, that would seem to indicate that the problem is not the cylinders.

Even so, does that mean that the problem could still be in the curl cylinders or not ?
No.
Or does that mean that the problem is elsewhere ?
1.Relief pressure is too low.
2.The load is too great.
And when I make the tests in post #4, and if the cylinders pass the tests, what then could the problem be ?
Without establishing cylinder drift with the control spool centered, post #4 tests are a waste of time.

And if it's a messed up valve in the control, is there any way to test for that ?

Connect both curl circuit hoses to the lift circuit QA connectors and the lift circuit hoses to the bucket circuit QA connectors.

 

[Arky217]

Connect both curl circuit hoses to the lift circuit QA connectors and the lift circuit hoses to the bucket circuit QA connectors.

Thank you RickB for the quick reply.

I think I see what you're saying to do.

So if I change the connections as you say,
then I assume the curl will be stronger and the lift will be weaker ?

So, is there a separate relief valve for the curl and a separate relief valve for the lift ?

How do I check the relief pressure and what should it be ?

Is the relief pressure valve (or valves, if one for curl and one for lift) located in the in the control assembly ?

Any way to check it without a pressure gauge ?

 

[RickB]

Thank you RickB for the quick reply.

I think I see what you're saying to do.

So if I change the connections as you say,
then I assume the curl will be stronger and the lift will be weaker ?
I believe your results will be the same as your experiences as posted in post #1.
So, is there a separate relief valve for the curl and a separate relief valve for the lift ?
No.
How do I check the relief pressure and what should it be ?
With a gauge. I can't quote the exact spec, it will be published in your operator manual.
Is the relief pressure valve (or valves, if one for curl and one for lift) located in the in the control assembly ?
I believe it is mounted on the hydraulic pump
Any way to check it without a pressure gauge ?Not with any degree of accuracy

Responses imbedded.

 

[Dave M7040]

The simple test is to swap the lines on your loader valve so that the lift arm circuit is controlling the bucket. If the problem goes away then you have determine the valve is the problem.

Dave M7040

 

[wdchyd]

The simple test is to swap the lines on your loader valve so that the lift arm circuit is controlling the bucket. If the problem goes away then you have determine the valve is the problem.

Dave M7040

If not .......then read reply #3