M6950 hydraulic issue

[TheOldHokie]

I need the serial number of the tractor as it appears from just the picture of the pump it's not the standard M6950.

One thing I have gleaned from the Blue prints it that does not have a normal three point setup.
It actually uses the lower three point arms to sense the weight on the arms and adjust the three point accordingly.
It's quite the elaborate setup.

Bear with us as we get more technical info to help you out.

Have you checked the lower lift arms (where they connect to the tractor) for any heavy wear or bearing issues?

Care to share?

Dan

 

[1fishinrogers]

I need the serial number of the tractor as it appears from just the picture of the pump it's not the standard M6950.

One thing I have gleaned from the Blue prints it that does not have a normal three point setup.
It actually uses the lower three point arms to sense the weight on the arms and adjust the three point accordingly.
It's quite the elaborate setup.

Bear with us as we get more technical info to help you out.

Have you checked the lower lift arms (where they connect to the tractor) for any heavy wear or bearing issues?

Bought new has never had any work other than I replaced 1 starter it has been incredibly reliable and has mowed thousands of rolls of hay. Wish I could find one brand new.

 

[North Idaho Wolfman]

Bought new has never had any work other than I replaced 1 starter it has been incredibly reliable and has mowed thousands of rolls of hay. Wish I could find one brand new.

I still need the serial number.

 

[North Idaho Wolfman]

Care to share?

Dan

Here is the sense bar assembly that works with the three point valve assembly.
I think it has to do with the more weight on the three point arms the more the valve moves.
I should have better answers here in a bit!

 

[1fishinrogers]

Here is the sense bar assembly that works with the three point valve assembly.
I think it has to do with the more weight on the three point arms the more the valve moves.
I should have better answers here in a bit!

View attachment 130020

K thanks I'm planning on going back into it tomorrow or Wednesday and will take a few pics as well

 

[TheOldHokie]

Here is the sense bar assembly that works with the three point valve assembly.
I think it has to do with the more weight on the three point arms the more the valve moves.
I should have better answers here in a bit!

View attachment 130020

When I saw that in the parts manual it struck me as being some form of mechanical lower link draft sensing but without any manuals its just a guess.

Lower link sensing (versus top link sensing) is popular on bigger AG tractors. I believe IH, Oliver, White, and Moline are some older examples of tractors with mechanical lower link draft control.

Big modern tractors do it electronically - Kubota M7 for example uses electronic lower link sensing.

I dont think the problem here is draft control related and would hope the OP has draft control disabled when doing his trouble shooting.

Dan

 

[North Idaho Wolfman]

When I saw that in the parts manual it struck me as being some form of mechanical lower link draft sensing but without any manuals its just a guess.

Lower link sensing (versus top link sensing) is popular on bigger AG tractors. I believe IH, Oliver, White, and Moline are some older examples of tractors with mechanical lower link draft control.

Big modern tractors do it electronically - Kubota M7 for example uses electronic lower link sensing.

I dont think the problem here is draft control related and would hope the OP has draft control disabled when doing his trouble shooting.

Dan

You might be right.

 

[1fishinrogers]

I still need the serial number.

 

[1fishinrogers]

I cannot make any sense out of his pressure tests. Rather than try and trouble shoot his trouble shooting I would like a simple statement of the problem.

Forget tje remotes for now. What is not working on the 3pt.?

When in position control does it lift a load when cold.

Does it stop lifting when hot?

Will it hold the load once its raised or does it bleed down.

Answer those three questions and post a picture of the gauge hookup and we will hopefully have a pathway forward.

Dan

The lift works fine cold or
You can run the tractor for an hour and if you don't move the lift control or move a remote level the pump pressure will remain at zero and you can at that point operate the lift and it will work fine for about 15 minutes then lose pressure
It will hold a load but arms will fall when the tractor is turned off

 

[TheOldHokie]

The lift works fine cold or
You can run the tractor for an hour and if you don't move the lift control or move a remote level the pump pressure will remain at zero and you can at that point operate the lift and it will work fine for about 15 minutes then lose pressure
It will hold a load but arms will fall when the tractor is turned off

OK - thats a good starting point.

You drilled and tapped the port in the hydraulic outlet cover where the gauge is installed?

Dan

 

[1fishinrogers]

OK - thats a good starting point.

You drilled and tapped the port in the hydraulic outlet cover where the gauge is installed?

Dan

No factory block with port

 

[TheOldHokie]

No factory block with port

OK - first order of business is to test the pump output pressure both hot and cold using the following procedure. Follow it exactly as written. Record the pressure readings here:

COLD PUMP DISCAHARGE PRESSURE TEST RESULTS

Pressure at Step 3: _____ PSI
Pressure at Step 4: _____ PSI
Pressure at step 5: _____ PSI

1. Start with tractor fully cooled down. Disconnect ALL implement hoses at the hydraulic outlets, place 3pt lift control in the full down position, and put draft control lever in disabled position.
2. Start engine and set engine RPM to approximately 2400 RPM
3. Read and record pressure at the gauge. It should be very close to zero
4. Operate the lever on the double acting remote control valve and hold it in the fulll open position. Read and record the pressure with the valve in that position. Factory specification is 2550 to 2850 PSI
5. Release the control lever on the remote valve and allow it to return to neutral. Read and record pressure. It should have returned to the pressure observed in Step 3.

Next is to repeat the test after the hydraulic system is fully warmed up. Do not operate any levers while waiting for the tractor to come up to temperature. Follow Steps 1 thru 5 exactly as you did the first time and make sure you use the same remote control valve. Record the results here:

HOT PUMP DISCAHARGE PRESSURE TEST RESULTS

Pressure at Step 3: _____ PSI
Pressure at Step 4: _____ PSI
Pressure at step 5: _____ PSI

Dan

 

[TheOldHokie]

No factory block with port

I have obtained a copy of the WSM and had a chance to skim through it. Here is the hydraulic system diagram. I have highlighted (RED) the portion of the system that the is being used for the pump discharge pressure tests. With the remote control valve (6) shifted the pump (4) output is deadheaded at the disconnected remote outlet (A) and the pump is unloading to tank via the main system relief valve.(5) The test eliminates all of the 3pt control system circuits and the results will tell us what the condition of the pump and relief valve are
.

Dan

 

[1fishinrogers]

OK - first order of business is to test the pump output pressure both hot and cold using the following procedure. Follow it exactly as written. Record the pressure readings here:

COLD PUMP DISCAHARGE PRESSURE TEST RESULTS

Pressure at Step 3: _____ PSI
Pressure at Step 4: _____ PSI
Pressure at step 5: _____ PSI

1. Start with tractor fully cooled down. Disconnect ALL implement hoses at the hydraulic outlets, place 3pt lift control in the full down position, and put draft control lever in disabled position.
2. Start engine and set engine RPM to approximately 2400 RPM
3. Read and record pressure at the gauge. It should be very close to zero
4. Operate the lever on the double acting remote control valve and hold it in the fulll open position. Read and record the pressure with the valve in that position. Factory specification is 2550 to 2850 PSI
5. Release the control lever on the remote valve and allow it to return to neutral. Read and record pressure. It should have returned to the pressure observed in Step 3.

Next is to repeat the test after the hydraulic system is fully warmed up. Do not operate any levers while waiting for the tractor to come up to temperature. Follow Steps 1 thru 5 exactly as you did the first time and make sure you use the same remote control valve. Record the results here:

HOT PUMP DISCAHARGE PRESSURE TEST RESULTS

Pressure at Step 3: _____ PSI
Pressure at Step 4: _____ PSI
Pressure at step 5: _____ PSI

Dan

I actually performed this test this morning but cold only and with no weight on the lift arms
The test went as follows lift and draft control down no remote connections
Cold start was zero and crept to 100psi after about a minute, held remote to full open at 2500psi released and returned to 100 psi I will perform again in the morning and test hot also

 

[TheOldHokie]

I actually performed this test this morning but cold only and with no weight on the lift arms
The test went as follows lift and draft control down no remote connections
Cold start was zero and crept to 100psi after about a minute, held remote to full open at 2500psi released and returned to 100 psi I will perform again in the morning and test hot also

Sounds good. The 100 PSI is a normal pressure drop (back pressure) across the remotes and 3 pt valves. Hopefully the hot numbers will be just as good.

If so we can give the pump and main relief a clean bill of health and move on to testing the 3pt portion of the circuit.

Dan

 

[1fishinrogers]

Sounds good. The 100 PSI is a normal pressure drop (back pressure) across the remotes and 3 pt valves. Hopefully the hot numbers will be just as good.

If so we can give the pump and main relief a clean bill of health and move on to testing the 3pt portion of the circuit.

Dan

Sounds good thanks

 

[1fishinrogers]

Sounds good. The 100 PSI is a normal pressure drop (back pressure) across the remotes and 3 pt valves. Hopefully the hot numbers will be just as good.

If so we can give the pump and main relief a clean bill of health and move on to testing the 3pt portion of the circuit.

Dan

Well it's took a little long but here's what I have
Cold test
Idle pressure 50
Open remote and held 10 seconds 2400
Idle 50

Hot test was all over the place
1st time
Idle didn't move the guage 0-5
Open remote valve 2000 held for 10 seconds and it fell to 1000 but then climbed back to 1500 and held
2nd time
Idle 0
Open remote 1900 after 10 seconds fell to 1300
Idle 0
3rd time
Idle 0
Open remote 1900 and held for 20 seconds and did not drop
Idle 0
Summary of problems
*Lift works perfect with no weight and or cold but drops immediately when engine stops
*New probem is the pto no longer works but I can hear a sound as if it is running internally but shaft doesn't move
*With weight on lift arms and or pto running(when working)Complete hydraulic failure after 15 minutes or less of use

 

[TheOldHokie]

Well it's took a little long but here's what I have
Cold test
Idle pressure 50
Open remote and held 10 seconds 2400
Idle 50

Hot test was all over the place
1st time
Idle didn't move the guage 0-5
Open remote valve 2000 held for 10 seconds and it fell to 1000 but then climbed back to 1500 and held
2nd time
Idle 0
Open remote 1900 after 10 seconds fell to 1300
Idle 0
3rd time
Idle 0
Open remote 1900 and held for 20 seconds and did not drop
Idle 0
Summary of problems
*Lift works perfect with no weight and or cold but drops immediately when engine stops
*New probem is the pto no longer works but I can hear a sound as if it is running internally but shaft doesn't move
*With weight on lift arms and or pto running(when working)Complete hydraulic failure after 15 minutes or less of use

Lets try to concentrate on one thing at a time. What did we learn from the pressure tests?

The pressure test shows pump delivery pressure is dropping significantly once the oil warms up and thins out.

The two most obvious causes would be a relief valve that is not seating properly and/or a worn pump that is bypassing internally.

Next steps would be to dissassemble, clean, and inspect the relief valve and pressure test the pump with the pressure relief out of the circuit.

Inspecting and cleaning the relief valve is the easiest of the two. A direct pressure test of the pump requires a different gauge hookup and a high pressure needle valve to control the flow.

Dan

 

[1fishinrogers]

Lets try to concentrate on one thing at a time. What did we learn from the pressure tests?

The pressure test shows pump delivery pressure is dropping significantly once the oil warms up and thins out.

The two most obvious causes would be a relief valve that is not seating properly and/or a worn pump that is bypassing internally.

Next steps would be to dissassemble, clean, and inspect the relief valve and pressure test the pump with the pressure relief out of the circuit.

Inspecting and cleaning the relief valve is the easiest of the two. A direct pressure test of the pump requires a different gauge hookup and a high pressure needle valve to control the flow.

Dan

K will do thanks

 

[TheOldHokie]

K will do thanks

I reread your description of the hot pressure test. Did you run that at engine idle speed? It should be run at 2400 RPM.

Dan