L**40 rear hydaulic pressure

[kuboman]

I guess that would explain the two different pressures.

I guess now the question is, what circuit are they tied too and where is the relief valve to control pressure in this circuit.

Does anyone have a hydraulic schematic for this model?

Roy

I have the service manual and the relief for the loader does the whole tractor. All the oil is channeled through the loader valve and the loader relief does it all. Soooo....can somebody please explain why I get 3200psi at the rear remote and 2600psi at the loader when both use the same relief??:confused2::confused2:

 

[dfkrug]

I have the service manual and the relief for the loader does the whole tractor. All the oil is channeled through the loader valve and the loader relief does it all. Soooo....can somebody please explain why I get 3200psi at the rear remote and 2600psi at the loader when both use the same relief??:confused2::confused2:

It makes no sense to me. The Lxx40s have only one implement pump,
set at about 2500psi. The rear AUX valves would have to be on an
entirely different circuit, with diff pump and relief valve. Pls explain
your method of testing the pressure.

 

[oldnslo]

Is this a gear pump and open center system? If yes is it possible that the rear remote DCV are plumbed in before the FEL control valve stack? If yes then your FEL relief will not see any pressure when using the rear DCV.

Just some thing to check if you trace the plumbing.

Roy

 

[kuboman]

It makes no sense to me. The Lxx40s have only one implement pump,
set at about 2500psi. The rear AUX valves would have to be on an
entirely different circuit, with diff pump and relief valve. Pls explain
your method of testing the pressure.

Tested the remote by plugging in a pressure gauge to the remote and then pulling the lever to bypass. Did the same with the loader. And there is only one circuit. The oil from the pump is fed to the loader valve and from there to the 3pt and rear remotes. I know it makes no sense but that is what it is doing. If someone can check theirs the same way would be good.

 

[Chilly807]

Something isn't quite right here... My L3400 with FEL has three separate OEM relief valves.

First is the main relief, located under the right side floorboard and controls the maximum pressure the pump puts out. ~2300 psi.

Next is the relief located on the loader valve, set at ~2250 psi.

Finally there is the relief located on the three point valve, which although I haven't checked, should be equal to or less than 2300 psi. Additionally, my aftermarket remote valve has a built in relief set at 2000 psi.

Unless the tractor is designed to operate at 3200 psi (highly unlikely), the main relief valve is not set correctly. The reason you don't see 3200 psi at the loader is because the loader valve is relieving properly at 2500 psi.

If the main relief were set properly, you wouldn't have 3200 psi available anywhere. Check your manual under the spec section, it should list max hydraulic pressure. There is a chance your main relief is set properly for 3200 psi, but I very much doubt it should be that high. If the dealer can't figure out how to adjust something that simple, you need to start looking for one that can.

The general rule of thumb is that each separate circuit (with directional valve controlling it) will have a relief valve adjusted to it's required maximum pressure limit.

Sean

 

[kuboman]

Something isn't quite right here... My L3400 with FEL has three separate OEM relief valves.

First is the main relief, located under the right side floorboard and controls the maximum pressure the pump puts out. ~2300 psi.

Next is the relief located on the loader valve, set at ~2250 psi.

Finally there is the relief located on the three point valve, which although I haven't checked, should be equal to or less than 2300 psi. Additionally, my aftermarket remote valve has a built in relief set at 2000 psi.

Unless the tractor is designed to operate at 3200 psi (highly unlikely), the main relief valve is not set correctly. The reason you don't see 3200 psi at the loader is because the loader valve is relieving properly at 2500 psi.

If the main relief were set properly, you wouldn't have 3200 psi available anywhere. Check your manual under the spec section, it should list max hydraulic pressure. There is a chance your main relief is set properly for 3200 psi, but I very much doubt it should be that high. If the dealer can't figure out how to adjust something that simple, you need to start looking for one that can.

The general rule of thumb is that each separate circuit (with directional valve controlling it) will have a relief valve adjusted to it's required maximum pressure limit.

Sean

The GL40's are designed with the loader valve integral with the tractor and it contains the only relief to the tractor. There is a safety valve for the 3 pt but it has nothing to do with anything else. The relief is set per the manual which I have been through many times. No one can explain the higher pressure at the back remotes but I am betting that every Gl 40 will do the same.

 

[oldnslo]

Kuboman,

First and foremost, you are correct it does not make any sense.

Does your service manual have a hydraulic schematic? Would like to see how it is supposed to work. Trying to determine how these valves are plumbed in series and how the Relief valve drains. Hopefully a seperate tank line Vs. the power beyond.

A long shot but something to maybe check if you haven't already. Is the power beyond feature in the FEL not installed properly so that what should be the tank line is being used as the power beyond? In this case operating your rear remotes would be pressuring the FEL tank line and the system relief would not work.

best of luck.

Roy

 

[kuboman]

Kuboman,

First and foremost, you are correct it does not make any sense.

Does your service manual have a hydraulic schematic? Would like to see how it is supposed to work. Trying to determine how these valves are plumbed in series and how the Relief valve drains. Hopefully a seperate tank line Vs. the power beyond.

A long shot but something to maybe check if you haven't already. Is the power beyond feature in the FEL not installed properly so that what should be the tank line is being used as the power beyond? In this case operating your rear remotes would be pressuring the FEL tank line and the system relief would not work.

best of luck.

Roy

As far as I can tell everything is plumbed correct. The return for the loader valve is dumped into the bottom of the tranny housing. The rear remote and 3 pt dump into the top of the tranny housing. The whole tractor is supplied by one pressure line from the pump to the loader valve and a line is taken from the LV to the auxiliary/3pt on the top of the tranny case. The by-pass/relief for the whole tractor is in the loader valve. Simple system but in my opinion somewhat inadequate. The only explaination I can cook up is that there is a certain amount of oil flow to the rear remotes that bypasses the relief. How else can you get higher pressure from one valve on the tractor than the other one when they both use the same supply and relief.?:confused2::confused2:

 

[oldnslo]

As far as I can tell everything is plumbed correct. The return for the loader valve is dumped into the bottom of the tranny housing. The rear remote and 3 pt dump into the top of the tranny housing. The whole tractor is supplied by one pressure line from the pump to the loader valve and a line is taken from the LV to the auxiliary/3pt on the top of the tranny case. The by-pass/relief for the whole tractor is in the loader valve. Simple system but in my opinion somewhat inadequate. The only explaination I can cook up is that there is a certain amount of oil flow to the rear remotes that bypasses the relief. How else can you get higher pressure from one valve on the tractor than the other one when they both use the same supply and relief.?:confused2::confused2:

Kubo,

A test that might give you a clue is:

Lower the FEL to the ground. Install your Gauge in the rear QD. Start raising the FEL and while the FEL is moving carefully bump the rear DCV to if either or both of the following happen:

1) Does the FEL Slow or stop moving when you bump the rear DCV?

2) Do see pressure on the rear QD?

If yes to either of these questions some thing is not plumbed or working like we think it is.

If the loader stops or stutters this would indicate youare blocking the flow either to or from the FEL valve.

If the pressure is again high in the rear QD's would be the same concern as previous answer. Some thing isn't plumbed correctly.

If NO to either one of the conditions above I would check theoretical pump flow by timing the FEL raise time. Measure actual cylinder stroke for a given period of time.

If you know bore sizes of cylinders we can calculate pump flow. Knowing measured pump flow should tell us if there is flow by-passing the FEL control valve.

I am attaching a fluid power formulae spread sheet for your reference. It has a formulae that can be transposed to back figure pump flow from cylinder speed and time.

hope this helps.

Roy

 

[slowzuki]

If you have a different pressure at the rear than at the loader, you must have more than one relief. There must be more to the hydraulic circuit than what you are seeing in the manual.