Weird FEL behavior

[oldnslo]

The rate of drop he described cannot be pressure equalizing in the cylinders. The valve has to be leaking internally if there are no external leaks, which he said there are not.

Agree a 100 percent on the continued drifting. Bad piston seals allows both ends of the cylinder to be under pressure which in effect doubles the leakage rate through the valve.

Initial drop I suspect is still pressure equalizing. High velocity oil (like leaks past seals) tends to aerate oil which will allow more movement that non-aerated oil

 

[ovrszd]

Agree a 100 percent on the continued drifting. Bad piston seals allows both ends of the cylinder to be under pressure which in effect doubles the leakage rate through the valve.

Initial drop I suspect is still pressure equalizing. High velocity oil (like leaks past seals) tends to aerate oil which will allow more movement that non-aerated oil

Yep. Hard to guesstimate how far that equalizing would allow the cylinders to move. But certainly not 2ft.

 

[83Ttype]

I pulled one cylinder off tonight and capped the lines coming from the tractor. The working cylinder seems to be holding pretty well so I will probably get the one I pulled off rebuilt. If I put it back together and it still has issues, I'll probably do the other one as well. They should cost around $100 each to get rebuilt so it isn't a big deal. Borrowing it saved me a LOT of $$ over the summer, so I want to make sure it is in good shape when I return it.

 

[Threepoint]

Good luck with this. Please report back on how things progress!

 

[3Lfarms]

Yep. Hard to guesstimate how far that equalizing would allow the cylinders to move. But certainly not 2ft.

In short, the hoses swell just a bit under pressure. Their volume does not stay the same as pressure is applied. The volume also changes as the hose is flexed. When straight, the hose has a larger internal volume than it does when it’s bent. The tighter the bend, the smaller the volume.

I keep seeing people say that the cylinder can’t compress even when the seals are bad.
I’m not saying this is OP’s problem, but there is more to the system than just the cylinders and the valve.

 

[Threepoint]

In short, the hoses swell just a bit under pressure. Their volume does not stay the same as pressure is applied. The volume also changes as the hose is flexed. When straight, the hose has a larger internal volume than it does when it痴 bent. The tighter the bend, the smaller the volume.

I keep seeing people say that the cylinder can稚 compress even when the seals are bad.
I知 not saying this is OP痴 problem, but there is more to the system than just the cylinders and the valve.

This is an interesting point, and certainly makes sense to me. But, on these CUTS, I'm wondering how much this fluctuation in internal hose volume during operations actually translates into observable changes in loader bucket or boom-arm orientation. :scratchchin: Would it be noticeable to the naked eye, as a practical matter?

 

[ovrszd]

In short, the hoses swell just a bit under pressure. Their volume does not stay the same as pressure is applied. The volume also changes as the hose is flexed. When straight, the hose has a larger internal volume than it does when it’s bent. The tighter the bend, the smaller the volume.

I keep seeing people say that the cylinder can’t compress even when the seals are bad.
I’m not saying this is OP’s problem, but there is more to the system than just the cylinders and the valve.

Are you saying hose deflection would allow 2ft drop? How big would a 3/4" hose hafta be to contain enough fluid for two cylinders to compress 2ft?

 

[83Ttype]

Fixed!!!

I had both lift cylinders rebuilt by the local hydraulic shop for $105 total (I expected a LOT more). Problem is completely fixed and the loader stops and stays exactly where you let off of the lever.

They did say that one of the cylinders was completely shot and the seal was "in pieces". I am guess that the reason it dropped while trying to lift "just a little" was that the fluid was leaking past faster than it was being fed into the cylinders.

Thank you all for the advice. It would have been a pain to replace the control valve, and wouldn't have fixed anything.

Shawn

 

[wdchyd]

:thumbsup:

 

[ovrszd]

Awesome!! So now if you lark it with the bucket in the air it stays there?