M120 with LA1601 loader, loader not working

[LOS]

So I'm trying to help my neighbor out with this tractor. he inherited it from his father in law. tractor was not running and the hydraulic pump was missing off it. honestly that's about all that is known.
some wiring repair and a new battery got it running. we installed a used (but known good) hydraulic pump, new filters and new fluid and fired it up. the tractor moves, power steering works, 3-point works and rear remotes work. however the loader was acting very erratic when you tried to raise it might go up or it might go down but would immediately stop and the hoses would jump and the motor would bog down. it acted like it was pressuring both sides of the cylinders at the same time.
long story short I rebuilt the loader control valve. I did find a blown O ring and the spool caps and detents were pretty rusty inside.
the spools moved freely and there was no scarring or anything, I installed all new O rings, new detent kits and new spool cap kits all bought from Kubota. everything went together without issue and I'm 99.9% confident I assembled everything correctly.
After reinstalling the control valve the loader is still not working correct. It has 2 different issues that I can identify.
1st when attempting to move the bucket in either direction the engine almost stalls and hear the pump like if it is dead headed and the bucket does not move at all, this issue was there before and after rebuild.
(when i loosen the lines at the cylinders only a little fluid comes out and the symptom is the same.)
2nd when trying to raise the boom if you pull back on the control lever 3\4 or less, the bucket will drop.
but if you pull it back all the way with mild force it will go up for a little ways then slow to a stop.
(if I loosen the opposite line on the cylinder the boom goes up normally)
I did not replace the relief valves on the loader control valve, they are a bit pricy and I'm not sure they would cause either issue.
I feel like I am missing something simple but I am at a loss, any help would be greatly appreciated.

 

[TheOldHokie]

So I'm trying to help my neighbor out with this tractor. he inherited it from his father in law. tractor was not running and the hydraulic pump was missing off it. honestly that's about all that is known.
some wiring repair and a new battery got it running. we installed a used (but known good) hydraulic pump, new filters and new fluid and fired it up. the tractor moves, power steering works, 3-point works and rear remotes work. however the loader was acting very erratic when you tried to raise it might go up or it might go down but would immediately stop and the hoses would jump and the motor would bog down. it acted like it was pressuring both sides of the cylinders at the same time.
long story short I rebuilt the loader control valve. I did find a blown O ring and the spool caps and detents were pretty rusty inside.
the spools moved freely and there was no scarring or anything, I installed all new O rings, new detent kits and new spool cap kits all bought from Kubota. everything went together without issue and I'm 99.9% confident I assembled everything correctly.
After reinstalling the control valve the loader is still not working correct. It has 2 different issues that I can identify.
1st when attempting to move the bucket in either direction the engine almost stalls and hear the pump like if it is dead headed and the bucket does not move at all, this issue was there before and after rebuild.
(when i loosen the lines at the cylinders only a little fluid comes out and the symptom is the same.)
2nd when trying to raise the boom if you pull back on the control lever 3\4 or less, the bucket will drop.
but if you pull it back all the way with mild force it will go up for a little ways then slow to a stop.
(if I loosen the opposite line on the cylinder the boom goes up normally)
I did not replace the relief valves on the loader control valve, they are a bit pricy and I'm not sure they would cause either issue.
I feel like I am missing something simple but I am at a loss, any help would be greatly appreciated.

You are indeed missing something simple and the control valve is the last thing to attack. You most likely have a flow restriction somewhere in the return circuit for the loader. This os a common issue with Kubota loader hydraulics. Common causes are bad quock conmects, improper plumbing, improperly adjusted 3pt feedback.

Since the remotes work amd the loadercwill operate when you remove the hose from the cylinder I woild suspect the quick coupler on the loader is not working.

Dan

 

[PoTreeBoy]

Check that the lines from the tractor to the loader valve are not crossed, specifically 010 and 020.

 

[LOS]

You are indeed missing something simple and the control valve is the last thing to attack. You most likely have a flow restriction somewhere in the return circuit for the loader. This os a common issue with Kubota loader hydraulics. Common causes are bad quock conmects, improper plumbing, improperly adjusted 3pt feedback.

Since the remotes work amd the loadercwill operate when you remove the hose from the cylinder I woild suspect the quick coupler on the loader is not working.

Dan

Thanks for the reply Dan I was told the same thing by a heavy equipment mechanic I happened to run into. we ordered new quick connects for it.

 

[LOS]

Check that the lines from the tractor to the loader valve are not crossed, specifically 010 and 020.
View attachment 150259

Funny you posted that picture I had just come across it yesterday. 10 and 20 are not crossed but 10 and 30 are crossed but they were that way before I took it apart. I know because I took pictures before taking it apart. I am going to switch them to where they are supposed to be but how much difference would it actually make?

 

[PoTreeBoy]

Funny you posted that picture I had just come across it yesterday. 10 and 20 are not crossed but 10 and 30 are crossed but they were that way before I took it apart. I know because I took pictures before taking it apart. I am going to switch them to where they are supposed to be but how much difference would it actually make?

I predict it'll solve some of the problem

 

[TheOldHokie]

Funny you posted that picture I had just come across it yesterday. 10 and 20 are not crossed but 10 and 30 are crossed but they were that way before I took it apart. I know because I took pictures before taking it apart. I am going to switch them to where they are supposed to be but how much difference would it actually make?

Now I am confused. I believe 10 and 30 are tank return and power beyond. Switching them would not affect the loader but the 3pt and remotes would not work ???

Dan

 

[Russell King]

Now I am confused. I believe 10 and 30 are tank return and power beyond. Switching them would not affect the loader but the 3pt and remotes would not work ???

Dan

@TheOldHokie
I am assuming that you are assuming the FEL valve is the original part.

If the valve was replaced with some “incorrect“ valve would there be some reason to swap 10 and 30?

 

[TheOldHokie]

@TheOldHokie
I am assuming that you are assuming the FEL valve is the original part.

If the valve was replaced with some “incorrect“ valve would there be some reason to swap 10 and 30?

The functions of those hoses are determined by the tractor hydraulic system not the valve.

Dan

 

[dvcochran]

So I'm trying to help my neighbor out with this tractor. he inherited it from his father in law. tractor was not running and the hydraulic pump was missing off it. honestly that's about all that is known.
some wiring repair and a new battery got it running. we installed a used (but known good) hydraulic pump, new filters and new fluid and fired it up. the tractor moves, power steering works, 3-point works and rear remotes work. however the loader was acting very erratic when you tried to raise it might go up or it might go down but would immediately stop and the hoses would jump and the motor would bog down. it acted like it was pressuring both sides of the cylinders at the same time.
long story short I rebuilt the loader control valve. I did find a blown O ring and the spool caps and detents were pretty rusty inside.
the spools moved freely and there was no scarring or anything, I installed all new O rings, new detent kits and new spool cap kits all bought from Kubota. everything went together without issue and I'm 99.9% confident I assembled everything correctly.
After reinstalling the control valve the loader is still not working correct. It has 2 different issues that I can identify.
1st when attempting to move the bucket in either direction the engine almost stalls and hear the pump like if it is dead headed and the bucket does not move at all, this issue was there before and after rebuild.
(when i loosen the lines at the cylinders only a little fluid comes out and the symptom is the same.)
2nd when trying to raise the boom if you pull back on the control lever 3\4 or less, the bucket will drop.
but if you pull it back all the way with mild force it will go up for a little ways then slow to a stop.
(if I loosen the opposite line on the cylinder the boom goes up normally)
I did not replace the relief valves on the loader control valve, they are a bit pricy and I'm not sure they would cause either issue.
I feel like I am missing something simple but I am at a loss, any help would be greatly appreciated.

Where are you getting the hydraulic supply/return for the loader valve(s)? If from the remotes on the back of the tractor the first thing I would do is test/replace the quick disconnects and make certain the poppets inside the quick disconnect are opening.
Some Kubota remote valves have a closed center position. This is particularly common on larter M series tractors.

 

[TheOldHokie]

Where are you getting the hydraulic supply/return for the loader valve(s)? If from the remotes on the back of the tractor the first thing I would do is test/replace the quick disconnects and make certain the poppets inside the quick disconnect are opening.
Some Kubota remote valves have a closed center position. This is particularly common on larter M series tractors.

See parts diagram earlier in thread. Open center system and loader valve with tank return and power beyond supplied by implement pump.

Dan