Hydraulics messed up ONLY when loader is on tractor

[J_J]

Just remove the hoses at the cyl and place in a bucket and check that flow is flowing when you push and pull the lever. This will check the QD's and flow from the work ports.

If you get the correct flow from the work ports, that will verify that the loader valve is working correctly.

Do you have a cyl connected to the same spool, and not crossed.

If you uncouple all QD's is everything working correctly?

Have you put a 3000 psi hyd gage in the hyd system yet.

 

[oldnslo]

Ok I have messed around with it some more and can say that this thing totally acts differently with the loader attached vs not attached. So the hydraulics are working great, attach the lines. Still working great. Move the bucket, things still seem okay. Lift the loader --- things go haywire. They will stay this way, but if I put the bucket down take off the lines to the bucket, the steering and 3 point return to normal. So there is something when I lift the bucket that messes it up. So that basically three things.

What do you think;

1. Something wrong with loader, its lines or one of the cylinders.
2. Something wrong with valve (this stays on tractor when I take the loader off)
3. Something wrong with one of the quick connects -- even though to my best knowledge they are working.

Guesses? How would I check? I am convinced it one of the three things listed.

Since things only fail when raising or lowering the loader this would point towards the directional valve spool for that function not working properly. If it returns to center the rest of the system should then operate. With the loader off or just disconnected and you move the directional valve lever and return it to center does everything still function? If no the problem is somewhere in the directional valve.

 

[J_J]

If he would just remove the hoses from the cyl and see if he has fluid flow for each position on the lever, he would see which hose or spool is giving trouble.

There is a logical process to trouble shooting.

He could also plug a gage into each end of the cyl hoses and see if there is pressure and how much.

 

[oldnslo]

If he would just remove the hoses from the cyl and see if he has fluid flow for each position on the lever, he would see which hose or spool is giving trouble.

JJ, how is hose on the loader cylinders going to make any difference on oil getting to the 3PH when the valve is supposed to be in the center condition?

There is a logical process to trouble shooting.

Agree very much with this. I just don't like removing hoses etc. until I feel the effort will result in answering a question. Also removing hoses is a good way to loosen dirt and introduce contaminates. We also don't know if these are pipe thread connections or JIC or SAE. Some times removing a hose is a very difficult and time consuming task.

From what the OP is describing it sounds like the lift spool is not centering properly. This could be from a worn or broken centering spring, linkage binding, corroded detent assembly if it has one, etc. By checking does the valve fail without the loader connected we have just taken one easy diagnostic step to potentially eliminate the loader QD's, hoses, etc.

Lot's of potential diagnostic steps. From my perspective the simplest is just unhooking QD's and see what happens. Then take the next step from there.

We also don't know what type of valve this is.
Is it a parallel - series circuit where oil from the lift circuit is directed to the curl/dump circuit.
Is it a parallel circuit: Where when using the lift and dump functions simultaneously the operation with the least load will operate first and the operator must feather the controls to do both functions in unison.
Does this valve have load holding checks built-in? Should not make any difference in the failure mode.
Does this valve have pressure compensation modules it in? These provide a consistent flow rate across the spool with load changes. If one of these stick they could also cause the flow to be blocked going down stream.

He could also plug a gage into the end of the cyl hose and see if there is pressure and how much.

respectfully

Roy

 

[J_J]

The point here is that if the 3pt works normally with the loader unplugged, and valve remains on the tractor, is that the fluid is still passing through the loader valve, whether the cyl hoses are plugged in or not.

It does not make sense that when he plugs in the hoses, things go bad.

He has not changed the flow path.

I can see a problem if the cyl work port hoses are switched.

I can also see a problem if the 3pt lever is in the up position and the fluid is being relieved which will cause back pressure and affect the loader operation.

I am just not sure he is doing all the checks we have mentioned.

A gage in a tee at the IN port of the loader valve would help a lot in trouble shooting the problem.

Final point here is, if all valves are in neutral, the pump flow should flow freely through all valves to tank. If the 3pt were blocking the flow, you would see it on the gage.

If the cyl hoses were crossed, and he tries to make a cyl move, one side of the cyl would be blocked because the fluid would be going to the other spool work port which is closed.

Long distance trouble shooting is difficult at best and I hope he gets the problem solved.

 

[Leejohn]

I'm going to put my 2c in. I also think it's not going to center, broken spring, or spool end has come unscrewed a little and giveing a false center.

 

[J_J]

If a spool is not centered, would not a cyl move to extend or retract.

He did not say anything about lift or curl cyl moving on their own.

 

[Leejohn]

I would think it would move and I'm not sure if he said anything about lift or curl cyl moving. can't remember.

 

[bulldogshotgun]

Ok I have messed around with it some more and can say that this thing totally acts differently with the loader attached vs not attached. So the hydraulics are working great, attach the lines. Still working great. Move the bucket, things still seem okay. Lift the loader --- things go haywire. They will stay this way, but if I put the bucket down take off the lines to the bucket, the steering and 3 point return to normal. So there is something when I lift the bucket that messes it up. So that basically three things.

What do you think;

1. Something wrong with loader, its lines or one of the cylinders.
2. Something wrong with valve (this stays on tractor when I take the loader off)
3. Something wrong with one of the quick connects -- even though to my best knowledge they are working.

Guesses? How would I check? I am convinced it one of the three things listed.

it appears at first glance to be a problem in the lift spool,

The point here is that if the 3pt works normally with the loader unplugged, and valve remains on the tractor, is that the fluid is still passing through the loader valve, whether the cyl hoses are plugged in or not.

It does not make sense that when he plugs in the hoses, things go bad.

He has not changed the flow path.

I can see a problem if the cyl work port hoses are switched.

I can also see a problem if the 3pt lever is in the up position and the fluid is being relieved which will cause back pressure and affect the loader operation.

I am just not sure he is doing all the checks we have mentioned.

A gage in a tee at the IN port of the loader valve would help a lot in trouble shooting the problem.

Final point here is, if all valves are in neutral, the pump flow should flow freely through all valves to tank. If the 3pt were blocking the flow, you would see it on the gage.

If the cyl hoses were crossed, and he tries to make a cyl move, one side of the cyl would be blocked because the fluid would be going to the other spool work port which is closed.

Long distance trouble shooting is difficult at best and I hope he gets the problem solved.

there are plenty of possible failures that could cause the flow to change through that valve when the hoses are attached,
he said its fine when he first connects it, but after attempting to raise the loader it messes up.
a PB valve with a sticking spool would do this (should also try to creep) or better yet a damaged spool, and the spool actually is returning to neutral but the load check is blocking flow out work port causing oil to return on tank line instead of PB.

 

[J_J]

Load checks sometimes cause weird problems.

You don't see a lot of data on bad load checks.

Does the fluid from a bad load check leak into the the return path?

Even is there is a bad load check, when the valve lever returns to neutral, the fluid in now only passing through the valve gallery to the next valve , and that is the 3pt.

Could the loader relief be stuck open and maybe some pressure is available?

I am still curious why a gage has not been used to verify or eliminate certain things.

Here is an alternative.

I am thinking a new valve would solve the problem.

http://www.surpluscenter.com/item.asp?item=9-7401&catname=hydraulic

http://www.surpluscenter.com/item.asp?item=9-8185&catname=hydraulic