valve rebuild.

[ch1ch2]

I have an issue with the lift valve on my NH TN95A. It has been leaking down for a while, it started falling fast or dropping while lifting, (I think float mode), and now it lifts so slow it is hard to get things done. I need to decide on rebuilding or replacing.
All advice is welcome. I will be away from my computer for awhile, so my replies will be slow.
I am going to take it apart this week.
I thought about swapping with a rear remote but the part numbers do not match and a big price difference so I am sure they are different valves.
Do I need to buy replacement seal rings between the valves?
Should I replace all the replaceable internal parts or just the ones I can see might be bad?
Any additional ideas?

 

[oldnslo]

First are you sure it is the valve? Do all other hydraulic functions operate properly and at the expected speed?

Usually if valves are worn to point they are leaking excessively they are not considered repairable.
Have you double checked the following:
Any linkage or cables operating this valve to be sure they are moving the valve spool and allowing it to spring return to the center or home position?

Checked for a corrosion or crud build up in the end caps covering the spools.

With FEL on the ground and engine off move the control lever and observe the spool travel. Does it travel similar distance in both directions?

Does the spool return to same center or home position repeatedly?

 

[cbailey1956]

Are you talking about the 3pt lift or the loader lift circuit? When you said "float" I assumed the loader lift. Anyway it could be a cylinder piston seal issue.

 

[bigdeano]

It's more likely the seal on a cylinder piston, not the valve.

 

[ch1ch2]

Thanks to all.
Yes, it is the valve!
Yes, it is the FEL.
Yes, the valve appears to work properly externally.
I removed the valve today. I should have it apart this weekend.

 

[cbailey1956]

Hopefully it will be in the detent cap area. Have repaired several that were dirty and the spool would not operate properly. Even had water trapped in several and they would freeze up in cold weather. Good luck

 

[wdchyd]

It's more likely the seal on a cylinder piston, not the valve.

X2.....

 

[Tx Jim]

Thanks to all.
Yes, it is the valve!
Yes, it is the FEL.
Yes, the valve appears to work properly externally.
I removed the valve today. I should have it apart this weekend.

Spool valve that is leaking internally must be replaced as a whole unit IE spool & housing because it is a "machined fit".

 

[LD1]

Spool valve that is leaking internally must be replaced as a whole unit IE spool & housing because it is a "machined fit".

x2

And if loader (as in lift arms and not just the bucket curl) are leaking down....it is NOT the cylinder seals. If there are no external (hoses, fittings couplers) leaking, than it IS the valve.

Spools are closely machined metal on metal valves. There are no seals to replace other than the end seals, which if bad would cause external hydraulic leaks.

 

[wdchyd]

And also to add to misery, if it ends up being a worn control valve you'll be doing some major housekeeping to clean up the gritty or rusty contaminated oil that could have contributed to spool wear.

 

[bigdeano]

Any update on what the problem was?

 

[jenkinsph]

Thanks to all.
Yes, it is the valve!
Yes, it is the FEL.
Yes, the valve appears to work properly externally.
I removed the valve today. I should have it apart this weekend.

How did you determine the valve was at fault?


Did you perform a leak down test with the cylinders and hoses isolated from the valve? That would be the first priority and quick and cheap to do. In most cases you can load the bucket raise it up a foot and prop it up with lumber. Unplug the quick couplers and back off the lumber, if it drifts back down the cylinder seals are the problem. If it stays up and does not drift down the valve is the problem and needs to be replaced with a new one.

 

[LD1]

How did you determine the valve was at fault?


Did you perform a leak down test with the cylinders and hoses isolated from the valve? That would be the first priority and quick and cheap to do. In most cases you can load the bucket raise it up a foot and prop it up with lumber. Unplug the quick couplers and back off the lumber, if it drifts back down the cylinder seals are the problem. If it stays up and does not drift down the valve is the problem and needs to be replaced with a new one.

You could totally remove the piston seals, and do as you describe, and as long as the hoses and QD's dont pour oil onto the ground, the cylinders aint gonna move and the loader WILL NOT drift.

For a loader to drift, the oil has to go somewhere OUTSIDE the cylinder

 

[ch1ch2]

UPDATE
I remove the valve and could not find a problem. I bought a new valve and installed it.
Read all the post in an other thread here on TBN. New I was on the right track with it having to be the valve.
Worked the tractor. Problem solved.
Wait...Not so fast. Problem is back but not as bad.
Lift is faster but not where I think is should be or once was. Bucket sometimes drops while lifting.
Reading the manual says pulling back on the joystick, valve goes in, loader goes up. Not the case!
This is a used tractor.
There is a ring on the joystick with blue and green indications on it. In one color position the bucket does not move with the arms going up and the other color position the bucket moves as the arms go up to keep the same orientation with the ground, or self leveling.
That self leveling feature was not on the tractor when I bought it.
I believe when it was taken off, they put the joystick on backwards. Swapping the hoses puts the up/down operations in the correct positions but the valve is moving in the wrong direction.
This would not be a problem on a simple valve, but my valve has a float feature for back dragging.
If I am correct, that is why the bucket drops while lifting.
It may also be why I think it is slow, if there is regen in it.
The manual does not say anything about regen but it describes a slightly different flow between lift and lower.
I should get around to reinstalling the joystick 180 degrees from its current mounting position this week.
Buying a new valve was a good thing. The arms do not drift down much at all now.
I may be wrong but I believe the lift speed should be somewhat closer to the lower speed.
Currently the lift speed is less than 1/4 of the lower speed.
After I get the float on the correct side of the joystick, hopefully the speed will increase. If not, then I will look at replacing the rod seals. UNLESS, someone here explains to me something I am missing.
A BIG Thanks to all of you for your input!

 

[muddstopper]

You could totally remove the piston seals, and do as you describe, and as long as the hoses and QD's dont pour oil onto the ground, the cylinders aint gonna move and the loader WILL NOT drift.

For a loader to drift, the oil has to go somewhere OUTSIDE the cylinder

It depends on which direction the cyl is mounted. The cyl shouldnt retract, even without a piston on the end of the rod because the oil cant compress. If the cyl is mounted so that the cy extends to lower the bucket, the rod can pull out of the barrel and the oil will pull apart and allow the bucket to fall. The piston seals would have to be bad for this to happen. It would depend on if there is enough weight hanging off the lift arms, but a loaded bucket could fall or at least creep down. I havent seen many loaders with cyl mounted in the method I mentioned, but I have seen a few so they are out there. Poor design that way, but it is what it is.

 

[LD1]

Turn that valve around and go from there. Some loader valves have some method of slowing down the drop speed of the loader, so it dont just slam to the ground if its got a heavy load. That method (restriction) may be the cause of the slow lift speed. But in either case, for your float to work, you need to turn the valve around.

After that, if you still experience the slow lift speed, it could indeed be the cylinders.

Lift cylinders will NOT cause a loader to drift. But it can indeed cause them to be slow and/or under powered.

To test if the piston seals are indeed leaking by causing your issue, you need to try to pick up something you know the loader will not lift. Chained to a stump, something heavy, etc. Make sure you CANNOT lift it. Put the loader up to it and put a little pressure on it. Unhook the loader hoses on the rod ends. Now attempt to lift again. If oil comes out the rod end ports, the piston seals are bypassing. If not....the cylinders aint your problem.

 

[LD1]

It depends on which direction the cyl is mounted. The cyl shouldnt retract, even without a piston on the end of the rod because the oil cant compress. If the cyl is mounted so that the cy extends to lower the bucket, the rod can pull out of the barrel and the oil will pull apart and allow the bucket to fall. The piston seals would have to be bad for this to happen. It would depend on if there is enough weight hanging off the lift arms, but a loaded bucket could fall or at least creep down. I havent seen many loaders with cyl mounted in the method I mentioned, but I have seen a few so they are out there. Poor design that way, but it is what it is.

I have personally never seen a loader that way.

Curl cylinders....yes. Loader cylinders....no.

For the purpose of 99% of the threads here on TBN about the subject, and all the current and future readers........a loader (as in lift and not curl) will NOT drift down due to faulty cylinder seals. I have no idea why this mis-information keeps getting spread.

 

[muddstopper]

UPDATE
I remove the valve and could not find a problem. I bought a new valve and installed it.
Read all the post in an other thread here on TBN. New I was on the right track with it having to be the valve.
Worked the tractor. Problem solved.
Wait...Not so fast. Problem is back but not as bad.
Lift is faster but not where I think is should be or once was. Bucket sometimes drops while lifting.
Reading the manual says pulling back on the joystick, valve goes in, loader goes up. Not the case!
This is a used tractor.
There is a ring on the joystick with blue and green indications on it. In one color position the bucket does not move with the arms going up and the other color position the bucket moves as the arms go up to keep the same orientation with the ground, or self leveling.
That self leveling feature was not on the tractor when I bought it.
I believe when it was taken off, they put the joystick on backwards. Swapping the hoses puts the up/down operations in the correct positions but the valve is moving in the wrong direction.
This would not be a problem on a simple valve, but my valve has a float feature for back dragging.
If I am correct, that is why the bucket drops while lifting.
It may also be why I think it is slow, if there is regen in it.
The manual does not say anything about regen but it describes a slightly different flow between lift and lower.
I should get around to reinstalling the joystick 180 degrees from its current mounting position this week.
Buying a new valve was a good thing. The arms do not drift down much at all now.
I may be wrong but I believe the lift speed should be somewhat closer to the lower speed.
Currently the lift speed is less than 1/4 of the lower speed.
After I get the float on the correct side of the joystick, hopefully the speed will increase. If not, then I will look at replacing the rod seals. UNLESS, someone here explains to me something I am missing.
A BIG Thanks to all of you for your input!

The lift will always be slower the lowering. The reason is because the push side of the cyl has a bigger space to fill than the rod (pull side) so it takes more oil to extend than retract. I do suspect that if your bucket is falling while lifting, then the valve may be hooked up backwards so that float in in on the lift instead of lowering. I would guess that to lift you have to pull the lever and you are probably pulling the lever far enough to put it in the float position. Had a neighbor complaining about his bucket dropping sometimes but not all the time. I asked him if he was pushing the lever all the way forward, his answer was f course. I asked if he realized his loader had a float built into his valve and if he pushed the lever all the way it would go into float mode and just drop. He didnt know he had float on the loader. I would suggest you confirm the valve isnt plumbed backwards before doing anything else. You can check for the float by gently lifting the bucket to raise and then see if pulling the joystick all the way back it should go into float and fall.

 

[muddstopper]

I have personally never seen a loader that way.

Curl cylinders....yes. Loader cylinders....no.

For the purpose of 99% of the threads here on TBN about the subject, and all the current and future readers........a loader (as in lift and not curl) will NOT drift down due to faulty cylinder seals. I have no idea why this mis-information keeps getting spread.

I will admit that a loader lift cyl should be mounted in a push instead of a pull position, but I have seen some old loaders that werent mounted that way. Also there are a lot of other equipment that do mount lift cyl on the retraction side of the cyl instead of the lift. The C frame on a lot of dozers, the boom on a lot of backhoes, some knuckle boom loader, just to name a few. No one is disputing your statements about cyl not retracting unless the oil has someplace to go outside the cyl. You are 100% correct, but I am also 100% correct that a cyl can extend without adding extra oil to take up the space lost as the rod exits the cyl barrel, while oil wont compress, it will expand. Will someone experience it using normal farm equipment with normal loads, with the cyl mounted to push rather than pull, probably not, but lift a backhoe bucket full of dirt with the lift cyl mounted to retract on lift, and let the piston come unscrewed from the rod and see how fast it will fall.

 

[muddstopper]

To keep it tractor related, heres a 3pt backhoe attachment with cyl mounted to lift on retraction, watch the video. , WM-76 7' Backhoe | Backhoe Attachments for Sale - WoodMaxx™