front bucket dropping overnight

[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.