L**40 rear hydaulic pressure

[kuboman]

Wow I think my head is going to expode:laughing:

To make any modifications to the loader valve involves getting lines made up plus removing the rear wheel and fender skirt to get at the valve. All the lines are formed steel. I did talk with the local dealer mech and he was talking with a Kubota service tech. So we will see if Kubota can figure this out. He had to admit that they never check the pressure at the rear remote it is always at the loader valve so this was all a surprise. Maybe something will come from it. I think somebody nailed it with the most logical explanation. Some oil is bypassing the relief and going straight to the PB port. :confused2:

 

[J_J]

Kuboman,

Are you reading this pressure at the remote or the 3pt?

Since the PB from the FEL valve is supposed to feed the 3pt, what pressure are you reading on the gage at the FEL valve, when you operate the 3pt lever to max? Theoretically it should be the same as the FEL, or could be set lower. However, more pressure to any hyd component will provide more force, more lift, more torque if hyd motor.

Are there instructions for setting the 3pt relief?

Are their instructions for setting the remote valve?

Does this tractor come with out FEL or remote, and if so, that means that the hyd pump is only feeding the 3pt. Curious what the pressure would be.

As far as fluid bypassing the relief and entering the hyd flow path, it seems like the pressure would dissipate in the fluid path to the remotes, and the fluid pressure would be low until the remote lever is activated, and even then the pressure is determined by the cyl load, or hyd motor if used .

Just how concerned are you about the 3200 psi if the cyl can handle the pressure?

When you are reading the 3200 psi, can you hear the pump straining or making any more noise than normal.

When you dead head the fluid into the gage, do you hear any kind of relief working, a whine, a screech, etc?

1 + 1 is not adding to 2 in this situation. I am still not sure we have all the facts. You can read different pressures on a series hyd line, but it is usually caused by the load.

You have not mentioned the remote relief valve, does it even have one?

In a series hyd circuit, the first valve with relief should limit the pressure to all the other valves, and therefore, the other valves down stream do not have to have a relief valve.

This situation you have now disputes that logic.

It would be good if more people with hyd knowledge would chime in here with their knowledge of hyd and help solve this mystery.

 

[J_J]

I sent the 5740 hyd pump number to Messick's and Kubota, and the answer came back.

John,

Kubota has told me that the max pressure is about 3,000 psi. Hope this helps.


Thanks!

Jeremy Ream
MESSICK'S
Parts Technician
800-222-3373 Ext-166
Direct # 717-367-0044
Messick's | Dealer for New Holland, Case IH, Kubota, Cub Cadet and More | Online Parts, Sales & Service.

 

[kuboman]

Kuboman,

Are you reading this pressure at the remote or the 3pt?

Since the PB from the FEL valve is supposed to feed the 3pt, what pressure are you reading on the gage at the FEL valve, when you operate the 3pt lever to max? Theoretically it should be the same as the FEL, or could be set lower. However, more pressure to any hyd component will provide more force, more lift, more torque if hyd motor.

Are there instructions for setting the 3pt relief?

Are their instructions for setting the remote valve?

Does this tractor come with out FEL or remote, and if so, that means that the hyd pump is only feeding the 3pt. Curious what the pressure would be.

As far as fluid bypassing the relief and entering the hyd flow path, it seems like the pressure would dissipate in the fluid path to the remotes, and the fluid pressure would be low until the remote lever is activated, and even then the pressure is determined by the cyl load, or hyd motor if used .

Just how concerned are you about the 3200 psi if the cyl can handle the pressure?

When you are reading the 3200 psi, can you hear the pump straining or making any more noise than normal.

When you dead head the fluid into the gage, do you hear any kind of relief working, a whine, a screech, etc?

1 + 1 is not adding to 2 in this situation. I am still not sure we have all the facts. You can read different pressures on a series hyd line, but it is usually caused by the load.

You have not mentioned the remote relief valve, does it even have one?

In a series hyd circuit, the first valve with relief should limit the pressure to all the other valves, and therefore, the other valves down stream do not have to have a relief valve.

This situation you have now disputes that logic.

It would be good if more people with hyd knowledge would chime in here with their knowledge of hyd and help solve this mystery.

Well I guess that is close to 3200psi. So does that mean the remote is not even bypassing and just maxing out the pump?

 

[J_J]

Somewhere in your manual, it should tell you how to check and reset the relief valves.

If they only mention one relief, then that is the only relief in the loader circuit. So if you plug in your gage anywhere within the loader to the 3pt circuit, you should see the loader relief pressure.

If that hyd pump is capable of 3000 psi, I don't see why they didn't set it to 2950 psi to gain the most power for the loader and 3pt.

 

[slowzuki]

I don't think people understand how the pump works, if it doesn't have a relief if you dead head it, it may make 5000+psi before it shears the shaft. Running it at more than the rated pressure will fatigue the shaft over time.

 

[oldnslo]

+1 on what slozuki said about the pump. Take them to far over rated pressure x number of times and something is going to break. drive shaft, gear case splits, etc. None of these are a desirable outcome.

Kuboman,

Are you willing to pick on few memory cells? If yes a few posts back you ran a test where you where curling the bucket and activating the rear remote. You stated the bucket curled and the pressure in the rear remote dropped. Do you recall if it dropped to zero or 200 or 500 PSI etc.

If you don't recall would you be willing to run the test again. If you can watch the gauge while curling the bucket back and then also when the cylinder dead heads. What if any pressure do you see on the rear remote while doing this?

If you are reading pressure under either or both conditions would you be willing to unhook the lift cylinder and then activate that function to force the oil over relief and then shift the rear remote with the oil going relief. Does the gauge in the rear remote read any pressure.

What I am trying to determine is if there is any flow/pressure coming through the FEL block under conditions when there should not be.

Does your FEL have self leveling? If yes is it hydraulic or mechanical self level?

Do you know if 4shorts tractor has self leveling or not?

If hydraulic self level it has to have valving that connects the raise and dump or lower and curl functions. I have never seen the schematic for the Kubota system and am not sure how it integrates onto the tractor. Logic says it should not cause higher system pressure but it doesn't seem like logic is working so far.

If you have the self level does the service manual cover this?

Remember, stubbornness will overcome common sense.....

Roy

 

[kuboman]

+1 on what slozuki said about the pump. Take them to far over rated pressure x number of times and something is going to break. drive shaft, gear case splits, etc. None of these are a desirable outcome.

Kuboman,

Are you willing to pick on few memory cells? If yes a few posts back you ran a test where you where curling the bucket and activating the rear remote. You stated the bucket curled and the pressure in the rear remote dropped. Do you recall if it dropped to zero or 200 or 500 PSI etc.

If you don't recall would you be willing to run the test again. If you can watch the gauge while curling the bucket back and then also when the cylinder dead heads. What if any pressure do you see on the rear remote while doing this?

If you are reading pressure under either or both conditions would you be willing to unhook the lift cylinder and then activate that function to force the oil over relief and then shift the rear remote with the oil going relief. Does the gauge in the rear remote read any pressure.

What I am trying to determine is if there is any flow/pressure coming through the FEL block under conditions when there should not be.

Does your FEL have self leveling? If yes is it hydraulic or mechanical self level?

Do you know if 4shorts tractor has self leveling or not?

If hydraulic self level it has to have valving that connects the raise and dump or lower and curl functions. I have never seen the schematic for the Kubota system and am not sure how it integrates onto the tractor. Logic says it should not cause higher system pressure but it doesn't seem like logic is working so far.

If you have the self level does the service manual cover this?

Remember, stubbornness will overcome common sense.....

Roy

First off I agree that to dead head a gear pump with no relief you will see some extreme pressures.
When I curl the bucket the pressure at the back drops to zero and when I bottom the cylinder and run the bypass I get zero at the back.
There is flow to the back with the loader in lift but that is how they designed the system.
It is not a self leveling loader and 4shorts will be the same.
I did hear back from the Kubota tech and he tried my tests with one on the dealers lot and got the same results as me more or less. 3200# at the back and about 2700# at the loader but they did there test with the engine revved. I get mine at idle. They could not explain what is going on though which was a disappointment. So I am not much wiser but somewhat relieved to know my tractor is how they are.
Strikes me as a serious design deficiency IMHO.
Still want it explained to me so my little brain can understand.:laughing:

 

[oldnslo]

First off I agree that to dead head a gear pump with no relief you will see some extreme pressures.
When I curl the bucket the pressure at the back drops to zero and when I bottom the cylinder and run the bypass I get zero at the back.
There is flow to the back with the loader in lift but that is how they designed the system.
It is not a self leveling loader and 4shorts will be the same.
I did hear back from the Kubota tech and he tried my tests with one on the dealers lot and got the same results as me more or less. 3200# at the back and about 2700# at the loader but they did there test with the engine revved. I get mine at idle. They could not explain what is going on though which was a disappointment. So I am not much wiser but somewhat relieved to know my tractor is how they are.
Strikes me as a serious design deficiency IMHO.
Still want it explained to me so my little brain can understand.:laughing:

I would like an explanation too, especially since 4shorts doesn't do this.

Can we blame it on you being cross eyed Canuks like Mace

Wish you the best since this defies all logic and physics.

Roy

 

[kuboman]

I would like an explanation too, especially since 4shorts doesn't do this.

Can we blame it on you being cross eyed Canuks like Mace

Wish you the best since this defies all logic and physics.

Roy

Cross eyed......yep, after this no wonder:drool: