front bucket dropping overnight

[rhunt]

Own an NX4510 hydro w/cab. When I leave the bucket raised somewhat after shutting down for the day and in the next morning find the bucket now on the floor. This is no big deal to me but would like to know what causes this. Just to be clear, this has happened since the tractor was new and there is no leaks in the system, meaning no oil anywhere on floor, just to be clear. Anyone have a cure? Bob

 

[Diggin It]

Dunno, but why leave it up? Should be dropping it to the ground for the safety of anyone or anything that happens to wander by.

 

[Wagtail]

Slow 'bleed down" of your FEL/3PH over a matter of hours is a normal occurrence. It's just weight + gravity + lack of maintained hydraulic pressure due to the hydraulic pump being shut off.

Rapid 'bleed down' would be a concern.

I never leave any implements raised over night or for an extended period. I put a couple of 4x4's under the bucket/forks and lower the FEL onto them, then work the joystick in all directions to relieve the pressure. A 3PH implement simply gets lowered onto its wheeled pallet at the same time. Out in the field (haying season), both simply get lowered onto the ground for overnight.

 

[prof fate]

every tractor does it.
I read the spec, for kubota i believe, is 1" drop per hour on a bucket. I think mine drops faster, but never timed/measure it - and the more weight the faster it drops, that I have observed.

Haven't seen my 3pt drop much - I know it drops some because it picks back up when the tractor starts to the setting on the control stick. the bucket/loader does not.

 

[rhunt]

Thank you for your replies. I usually lower the bucket just as you all have done and know this is good practice, I was just wondering, that's all. Thanks again, Bob

 

[K5lwq]

The directional control valve leaks internally. Some valves bypass more than others. If you have bad seals in the cylinder, it would fall even faster. As long as you don't see any external leakage, and the leak down doesn't bother you, I would not worry to much. :thumbsup:

 

[ovrszd]

Definitely control valve leakage.

Impossible for the cylinders to cause this type of leakage. The internal cylinder seals aren't doing anything is this scenario.

My Kubota leaks down a little.

My 35 year old Ford doesn't leak down at all.

So, every tractor does not do this.

No worries if it doesn't affect operation.

 

[Highgear]

I always put the bucket all the way down and curled up so none of the shiny part of the cylinder is exposed . My cylinders are not going to rust . Last thing I do after it's shut down is to move the stick in a round motion to take the pressure off everything .

 

[RickB]

Definitely control valve leakage.

Impossible for the cylinders to cause this type of leakage. The internal cylinder seals aren't doing anything is this scenario.

My Kubota leaks down a little.

My 35 year old Ford doesn't leak down at all.

So, every tractor does not do this.

No worries if it doesn't affect operation.

Piston seal leakage is often the cause of cylinder drift. More often than not manufacturers have an allowable drift spec published that gives them more than sufficient wiggle room to dodge all but the most egregious drift complaints. There is no doubt this is more of a problem with newer equipment than older.

 

[ovrszd]

Extending cylinder drift can be leakeage within the cylinder. Collapsing cylinder drift cannot be caused by leakage within cthe cylinder. The rod cannot go into the barrel because the fluid cannot be compressed. So collapsing drift can only happen if there is an external leak or valve leakage.

 

[K5lwq]

Here is a great demo that shows what a cylinder with bad seals will do. I think if the cylinder is fully extended then it could not collapse. This is always a fun debate. :laughing
Hydraulic cylinder fluid internally bypassing - YouTube

 

[ovrszd]

Excellent demo.

Shame he didn't demo the other way, which would have proved my theory that cylinder retraction drift cannot happen without an external leak or a bad valve.

Using his theory, if the OP's cylinders are bad, his FEL should have raised.....

 

[VictorW]

My 2004 CK30hst has always done that. I doubt very much there is any problem with the cylinders or it would drop much faster. More than likely it is the control valve but there is nothing wrong with it. If you ever had a control valve apart, there is the valve block itself with round rod type control spools that move back and forth within the bored round holes in the valve block. The clearances are very tight but still enough difference between the hole diameter in the block and the diameter of the round spool rod so it can move. There are seals but these are at each end of the valve block that seal the spool so no fluid escapes out of the valve block itself. So I don't believe there is anything to worry about. It's just how the control valve block is designed.

 

[RickB]

Extending cylinder drift can be leakeage within the cylinder. Collapsing cylinder drift cannot be caused by leakage within cthe cylinder. The rod cannot go into the barrel because the fluid cannot be compressed. So collapsing drift can only happen if there is an external leak or valve leakage.

My experience is contrary to your opinion. We can leave it at that.

 

[K5lwq]

We know the OP doesn't have a problem and that the internal valve leakage is why his loader drops over night. The question of cylinder drift was introduced merely to explain some of the causes.

Rick is correct. More often than not, rebuilding the cylinders will reduce drift back to an acceptable level. The reason is because, with bad piston seals, not only is the load side of the spool bypassing but also the return side. This will cause the drift to be much more noticeable.

Replacing the valve could make it worse if the new valve has a higher internal leakage value. Most valve manufacturers will put this information in their spec sheets. :drink:

 

[ovrszd]

My experience is contrary to your opinion. We can leave it at that.

I am very respectful of your opinion Rick. Explain how the ram can go into the barrel and displace fluid without an external leak or a bleeding valve?

 

[ovrszd]

We know the OP doesn't have a problem and that the internal valve leakage is why his loader drops over night. The question of cylinder drift was introduced merely to explain some of the causes.

Rick is correct. More often than not, rebuilding the cylinders will reduce drift back to an acceptable level. The reason is because, with bad piston seals, not only is the load side of the spool bypassing but also the return side. This will cause the drift to be much more noticeable.

Replacing the valve could make it worse if the new valve has a higher internal leakage value. Most valve manufacturers will put this information in their spec sheets. :drink:

See above post.

It's simply impossible in regards to a collapsing cylinder. Opinions cannot overcome science.

 

[4570Man]

My experience is contrary to your opinion. We can leave it at that.

It’s not opinion it’s fact. Go stick your arm in a bowl of water that’s full to the brim and not spill any. It’s possible that leaky seals would make the loader drop faster but the valve would still be source of the problem. My logic behind this theory is the bad piston seals would reduce the surface area significantly increasing the psi to hold the same load and higher pressure fluid is going to leak past the valve faster.

 

[K5lwq]

If there is no where for the fluid to go then yes it could not collapse. However, if you have a lift cylinder that has bad seals, you can disconnect and cap the pressure side and the load will still fall. As the fluid bypasses the seal it forces fluid back through the valve. This does not prove the valve is out of spec, but proves the seals are bad.

By fixing the cylinder the fluid only has one path back to tank which most of the time is back in spec of the valves performance.

Let's say the valve manufacturer claims a 12 CC per minute leakage rate. If the piston seal is bad, then the rate would be 24 cc per minute. Doesn't take long at that rate for the load to be on the ground.

Is that a fair assumption?

 

[ovrszd]

Took me awhile to swallow this fact. I thank LD1 for helping me to understand it.