hydro curling on own

[jkfromk]

I have a NH 1925 with FEL and lately it seems to try to curl the bucket on its own. It doesn't always do it but all of a sudden it will start doing it's on it's own. It seems the control is very sensitive from left-to-right.

Any ideas? I was thinking leak however I don't see any signs on any of the lines or connections.

Thank you in advance!

 

[J_J]

The spool for the curl may not be centered. Clean the spool and springs. Look for any debris causing the spool not to center.

 

[AKKAMAAN]

sounds like a leaking piston seal to me.....if curl means cylinder extend....

 

[J_J]

The poster did not say whether up or down. Since he said the lever was sensitive, I am thinking that the there might be some dirt/trash in the neutral position. Might also be the linkage binding.

Intermittent leaking, perhaps.

 

[Mechanos]

sounds like a leaking piston seal to me.....if curl means cylinder extend....

Even if a piston seal was leaking... it wouldn't curl on it's own if the spool valve were functioning properly. I agree with JJ... the problem is in the spool valve.

 

[jkfromk]

Sorry, yes, it is curling down on it's own. Is it possible to have a leak with no visible signs of fluid?

Also, please forgive my ignorance but is the spool the box under the control lever/joystick? If so, I will take a look at it today and see what I find.

I appreciate the help so far!

 

[wdchyd]

Sorry, yes, it is curling down on it's own. Is it possible to have a leak with no visible signs of fluid?

!

Yes......Cyl packings can leak internally without any visible signs of fluid

 

[J_J]

This is a Prince loader valve. Look at pages 4 and 5. You can see the spools and the lever, or handle kits assembly.

http://www.princehyd.com/Portals/0/products/valves/LVManual.pdf

 

[jinman]

If the loader has quick connects, I'd curl the bucket up and then pop off both QCs. If the loader bucket continues to go to dump, then there is a leaking cylinder. If the loader bucket holds or substantially slows, the problem is probably a dirty spool or return to center spring on the joystick valve.

JkfromK, you didn't say how fast the bucket dumps and if you can stop the action by forcing the joystick to neutral. Those details would sure help. It DOES sound like a dirty spool to me because you indicated the problem comes and goes. Normally a leaky cylinder seal will come and stay.

 

[jkfromk]

JJ - thanks for the diagram. I can pull the spool out w/o losing lots of hydro fluid? Just pull them and spray with something like brake cleaner?

They do have quick connects. Will try that and report back. It tries to dump very slowly, would take a minute or so for full dump. If I pull stick all the way back it stops. If I carefully center the stick it will hold but when it gets even a bit bumpy it starts again. I have to essentially keep my hand on it to keep it centered.

 

[J_J]

Do you let the valve lever spring back to neutral, or do you gently let it go to neutral. I still think it is trash associated with the spool assembly. Clean and lube both ends of the valve.

 

[J_J]

JJ - thanks for the diagram. I can pull the spool out w/o losing lots of hydro fluid? Just pull them and spray with something like brake cleaner?

They do have quick connects. Will try that and report back. It tries to dump very slowly, would take a minute or so for full dump. If I pull stick all the way back it stops. If I carefully center the stick it will hold but when it gets even a bit bumpy it starts again. I have to essentially keep my hand on it to keep it centered.

You are confusing me here. Curl is usually left right on the joystick valve if that is what you have. The holding back on the valve stops the curl doesn't make sense. Centering the valve stops the curl.

Does the FEL valve have regen? You know, push right and more right for regen/fast dump. .

Does the bucket ever curl up by itself?

Does the curl function go through a full cycle?

That bucket should curl up or down in a few seconds. Check those QD's again. They might be fouled . Try this, remove the QD's from the hose going to the curl cyl's, and connect the male and female together, and place in a bucket and see if you have good hyd flow, and if not, replace the QD's.

Also check the bottom attachment on the spool and ensure the spool centering springs and stops are tight.

 

[AKKAMAAN]

Even if a piston seal was leaking... it wouldn't curl on it's own if the spool valve were functioning properly. I agree with JJ... the problem is in the spool valve.

Mechanos! I did not say J_J was wrong. I said that leaking piston seals can cause drift even if spool valve is perfectly centered.

I think this is one of the most common myth's in hydraulics.

Mechanos! Study my drawings below.

The cylinder can extend from gravity if piston seal leak, the only pressure that will hold the piston (rod) back is the atmospheric pressure.
Volume on rod side of piston is less than the capped side....This is a very common effect from leaking piston seals.
If gravity would push the piston in, retract there will be pressure intensification, cylinder piston (rod) will hold up until pressure open the work port relief or break something...

Like jinman says, it is also important to take into account how fast it leaks down too....but still, most FEL's curl down on cylinder extend,

and it ends up to be the "wear part" in the system that have failed...the piston seal.

This bucket curl down on cylinder retract.

Another possibility is if there is an inline regen valve involved

See the difference between the two cases on these two pictures

 

[jkfromk]

Well I was finally able to tear it down and get a first hand look at the issue. Travel and kids sports kept me away but now happy to report back.

Upon inspection of the whole valve (spool?) assembly I noticed one of the bolts was missing from the bottom cap. It had come loose and was thankfully still wedged between the hard lines of the hydros. The missing bolt was allowing the cap to sag and thus not engage the spring to push the stick back to center.

I ended up taking the other bolt off, inspecting it for debris and put it back together. It was not easy trying to work behind the hard lines however with some patience and finger acrobatics I got it back together. It now works great.

Thanks for all the input, it gave me some confidence and direction on the fix! Now, is there a trick to working on that thing w/ those lines in place? A special tool perhaps?

 

[jkfromk]

You are confusing me here. Curl is usually left right on the joystick valve if that is what you have. The holding back on the valve stops the curl doesn't make sense. Centering the valve stops the curl.

Does the FEL valve have regen? You know, push right and more right for regen/fast dump. .

Does the bucket ever curl up by itself?

Does the curl function go through a full cycle?

That bucket should curl up or down in a few seconds. Check those QD's again. They might be fouled . Try this, remove the QD's from the hose going to the curl cyl's, and connect the male and female together, and place in a bucket and see if you have good hyd flow, and if not, replace the QD's.

Also check the bottom attachment on the spool and ensure the spool centering springs and stops are tight.

Yep that was it! Thanks for all the input. I sincerely appreciate it.