FEL Hydraulic Hookup Questions

[jacksork]

Tractor is a L295DT. Loader I think is a L1200 series (Can't confirm 100% but the hydraulic piston seals are the same part number as that series).

Currently the input for the loader valves comes from the hydraulic output block (listed as that in the parts manual, service manual lists it as the oil pressure block)

The output then goes to what I believe is the low pressure side of the hydraulic output block that gets routed back into the tank.

The power beyond port (edit: incorrect adapter so not actually PB) is hooked up back to the tank.

My confusion is why is the power beyond routed back to the tank? Shouldn't it be at high pressure? (edit: incorrect adapter so not actually PB)
What am I not understanding/missing?

 

[Dave_eng]

Tractor is a L295DT. Loader I think is a L1200 series (Can't confirm 100% but the hydraulic piston seals are the same part number as that series).

Currently the input for the loader valves comes from the hydraulic output block (listed as that in the parts manual, service manual lists it as the oil pressure block)

The output then goes to what I believe is the low pressure side of the hydraulic output block that gets routed back into the tank.

The power beyond port is hooked up back to the tank.


View attachment 47679

My confusion is why is the power beyond routed back to the tank? Shouldn't it be at high pressure? What am I not understanding/missing?

There are a couple of design features to bring to your attention

The loader valve has its own relief valve which, to operate properly needs to be able to vent back to the tank or reservor.

The power beyond output from the loader vale is fed back into the block to provide hydraulic power to the 3 pt hitch and rear remotes if any..

The diagram is correct except regarding what is happening inside the block. Inside the block, the pump output is directed to the loader IN port.

The loader PB port is just returning the availability of high pressure oil to the block to continue to the 3 pt.

I know the WSM description of which port is for what on the block is confusing

Ask more questions if this is not clear.

Dave

 

[jacksork]

The power beyond output from the loader vale is fed back into the block to provide hydraulic power to the 3 pt hitch and rear remotes if any..

So should the Power Beyond connection go back to the hydraulic block then instead of the port on the top of the tank? Should the loader output hose and PB hose be switched on its connections at the tractor?

 

[Dave_eng]

So should the Power Beyond connection go back to the hydraulic block then instead of the port on the top of the tank? Should the loader output hose and PB hose be switched on its connections at the tractor?

Lets start with how do you know which port is which on the loader valve.

Often a tank port will have a sleeve or plug installed in it to make it a power beyond port.

Dave

 

[jacksork]

So an outlet that is just marked PB may not function as PB if it doesnt have one of those?

(edit: incorrect adapter so the port does not function as PB)

 

[Dave_eng]

So an outlet that is just marked PB may not function as PB if it doesnt have one of those?

Unless we are talking about valves installed as part of a new tractor by the manufacturer, generally manufacturers of hydraulic valves and loader valves sell them without power beyond installed. They offer the PB upgrade as a buyer installed option. In such cases the valve will have two T ports. One of these ports will be modified to become a PB port.

Does your valve have PB cast into the valve body?

Is your loader not working correctly or are you just trying to understand it fully?

Dave

 

[jacksork]

Kind of both. Loader is working, however the 3pt cannot lift a load, it was proposed on other threads to confirm that the loader was plumbed correctly so I was trying to track that down. I also would like to have a better understanding of tractor hydraulics.

I just got off the phone with Prince Tech Support and my specific valve had the PB port blocked off.

Back to the loader valve I took off the plumbing bushing that was installed and there was not a hex bushing on the inside or the other adapter plug you showed so it was essentially another low pressure output.

 

[jacksork]

So my question now would be if having (2) hoses back to the tank could possibly have an effect on the pressure available to the 3 pt hitch? The 3pt hitch will lift, it just cant do it with a load on it?

 

[Dave_eng]

So my question now would be if having (2) hoses back to the tank could possibly have an effect on the pressure available to the 3 pt hitch? The 3pt hitch will lift, it just cant do it with a load on it?

Your comment: my specific valve had the PB port blocked off is not clear to me. Does your valve have PB or not?

Can it have PB added if it is not there?

Both loader valve tank ports have hoses connected. One of these hoses goes directly to the transmission aka tank.

The other loader valve tank port hose goes back to the hydraulic block.

The 3 pt hitch is receiving fluid but at not sufficient pressure to be able to lift a load. Typically less than 500 psi.

Without the proper PB valve fitting the loader valve is only supplying the 3 pt hitch with oil at low pressure.

To answer your question, having the loader valve feed the 3 pt hitch without the optional PB fitting will never work properly

Dave

 

[jacksork]

The valve currently does not have the PB installed. It can be added if I get the correct adapter.

As it is if I install a plug where the PB port is on the valve and only have the inlet and outlet hose to the hydraulic block, the tractor is hard to start and runs at a noticeably lower idle and the loader will not operate correctly. If I put the hoses back as it was the tractor operates at its typical idle and the loader functions.

Also as it was (as of last week) I had replaced the missing part (the rod that connected the control valve to the position/feedback rod) and the 3pt arms would lift if there was no load on them. If the speed valve under the seat was locked it would hold a load, but as soon as you unlocked it it would drop.

 

[Dave_eng]

The valve currently does not have the PB installed. It can be added if I get the correct adapter.

As it is if I install a plug where the PB port is on the valve and only have the inlet and outlet hose to the hydraulic block, the tractor is hard to start and runs at a noticeably lower idle and the loader will not operate correctly. If I put the hoses back as it was the tractor operates at its typical idle and the loader functions.

Also as it was (as of last week) I had replaced the missing part (the rod that connected the control valve to the position/feedback rod) and the 3pt arms would lift if there was no load on them. If the speed valve under the seat was locked it would hold a load, but as soon as you unlocked it it would drop.

A hydraulic lesson in basic system design. Your Kubota has an Open Center hydraulic system using a fixed displacement pump.

Contrast this with a Closed Center system where the pump has a variable displacement feature where the pump output can go from 0 to maximum flow in response to the demand for hydraulic power.

In a properly plumbed open center system, oil is continuously circulating from the reservoir to the pump, through the pump, through a control valve and back to the reservoir. The quantity of flow is a simple function of pump rpm.

Until there is a demand for hydraulic action by moving a loader lever or a 3 pt lever, the pressure in the circulating oil is very low and the pump needs little power to turn it. The movement of a valve lever directs the flow into a dead end cylinder, a loader cylinder or a 3 pt cylinder and because the flow is dead ended the pressure rises quickly. A relief valve limits how high the pressure can rise.

To allow it to rise without relief valve protection will quickly destroy the pump.

I urge you not to run your tractor until the plumbing is sorted out. Hydraulics are not a lets try it and see what happens situation. In a fraction of a second a very expensive and perhaps difficult to replace pump or valve is split and destroyed.

The hard starting and slow idle are your only warning!!! Take heed.

Start moving forward by posting brand and model number of the loader valve.

Post marked up photos of the hydraulic block indicating which hose goes where.

Post photos of the loader valve so the cast in letters for the various ports are visible.

Dave

 

[jacksork]

Valve is a Prince RD522GCGA5A4B1:

Here is the diagram of how the tractor is currently plumbed.

Here is a picture of the actual loader valve:

(Disclaimer: what I describe next I did before seeing your message)

It was previously suggested by a mechanic that I try moving the loader and the 3ph at the same time to see if the 3ph would raise with a load on it.

I tried various combinations and if I lower the bucket from a completely raised position with the 3ph in a lift and have the engine moderately rev'd the 3ph would raise slowly with a 300lb load on it. If I wanted to raise it more I would have to raise the bucket again and repeat.

 

[jacksork]

Here is the attachment of the hoses to the transmission port & hydraulic block:

Here is a closeup of the hydraulic block:

 

[jacksork]

Question:

-the stock hydraulic block cover (PN 35300-36720), does it block off the top ports on the hydraulic block, or is it meant to keep the flow through the hydraulic block?

 

[Dave_eng]

I need to take some time to study the info you have added.

Usually, an optional block cover is needed but let me check further.

Within the optional block the high pressure oil is blocked and sent to the loader valve. The high pressure oil leaves the loader valve via its power beyond port and returns to the opposite isolated side of the hydraulic block so it can be utilized by the 3 pt hitch.

Dave

 

[Dave_eng]

More history would be helpful.

Was the tractor operating properly until the loader valve was changed or what happened?

You have to get the required PB fitting for your Prince valve or the 3 pt hitch will only be fed with low pressure oil which could only be 500 psi or less.

The PB line needs to go to the block not the transmission

If you get and install the PB fitting and change which line connects to the block I think your problem will be solved.

Dave

 

[torch]

Valve is a Prince RD522GCGA5A4B1:



Here is the diagram of how the tractor is currently plumbed.
View attachment 47733

Does the outlet beside D (now connected to the Pressure Block/Hydraulic Block) have one of these installed: https://www.surpluscenter.com/Hydra...r-Beyond-Sleeve-Prince-660312004-9-4895-B.axd ?
If not, then buy one of those, install in the PB port, and switch the hoses so PB goes to hydraulic block and the one currently connected to the HB goes to the tank.

 

[torch]

Take the 4 bolts out of the hydraulic block and verify that the flow is forced from the pump through 2 and returns from PB to 3 and that there is no way for fluid to flow from 2 to 3 without going through the FEL valve.

 

[jacksork]

More history would be helpful.

Was the tractor operating properly until the loader valve was changed or what happened?

You have to get the required PB fitting for your Prince valve or the 3 pt hitch will only be fed with low pressure oil which could only be 500 psi or less.

The PB line needs to go to the block not the transmission

If you get and install the PB fitting and change which line connects to the block I think your problem will be solved.

Dave

History would be helpful and unfortunately there isn't much I know for sure. Supposedly the tractor was used on a farm and the 3pt stopped working. It didn't have a loader from the previous owner's previous owner. The previous owner pulled the loader from a non working l295DT.

Moral of the story is negating the loader, the 3pt couldn't have worked because of the missing control valve lever. I installed a replacement and the 3 pt then would go up and down without load. Based on previous suggestions the proper plumbing of the loader needed to be confirmed/clarified.

Thanks for advice. I suspected that was the issue and I have the correct PB fitting on hand and am going to try it today.

 

[jacksork]

Take the 4 bolts out of the hydraulic block and verify that the flow is forced from the pump through 2 and returns from PB to 3 and that there is no way for fluid to flow from 2 to 3 without going through the FEL valve.

Correct the ports 2 and 3 are not connected in the block and it would have to go through the FEL.