M7040 3 point weakens throughout the day

[Mikec575]

My M7040 3 point will pick up implements in the morning and after lunch I have to bring the RPM up to get it to lift the same weight it lifted before lunch at an idle.
any suggestions?
comparison- M7060 will lift the back of my gooseneck no problem and the M7040 barely lifts it when bringing the RPMs up.

 

[TheOldHokie]

My M7040 3 point will pick up implements in the morning and after lunch I have to bring the RPM up to get it to lift the same weight it lifted before lunch at an idle.
any suggestions?
comparison- M7060 will lift the back of my gooseneck no problem and the M7040 barely lifts it when bringing the RPMs up.

Something in your hydraulic system is bypassing oil when the oil warms up and thins out. The two main suspects are the 3pt lift cylinder and/or the hydraulic pump. Do you have a loader on the tractor?

Dan

 

[Mikec575]

My M7040 3 point will pick up implements in the morning and after lunch I have to bring the RPM up to get it to lift the same weight it lifted before lunch at an idle.
any suggestions?
comparison- M7060 will lift the back of my gooseneck no problem and the M7040 barely lifts it when bringing the RPMs up.

Something in your hydraulic system is bypassing oil when the oil warms up and thins out. The two main suspects are the 3pt lift cylinder and/or the hydraulic pump. Do you have a loader on the tractor?

Dan

No sir I do not have a loader on it

 

[TheOldHokie]

No sir I do not have a loader on it

I would suggest a couple simple tests. Conduct each test before the oil is warmed up and again after its warmed up and you are loosing lift.

1. Check for cylinder bypass. Remove the small return hoses on the lift cylinders and check for fluid when you raise a heavy load. Ideally there should be none.
2. Measure pump pressure. Plug a pressure gauge into your rear remote and operate the control lever to get a pressure reading. Factory specification is 2770 PSI.

 

[Mikec575]

I would suggest a couple simple tests. Conduct each test before the oil is warmed up and again after its warmed up and you are loosing lift.

1. Check for cylinder bypass. Remove the small return hoses on the lift cylinders and check for fluid when you raise a heavy load. Ideally there should be none.
2. Measure pump pressure. Plug a pressure gauge into your rear remote and operate the control lever to get a pressure reading. Factory specification is 2770 PSI.

How can I go about seeing if it is bypassing in the steering system?
I am only getting about 1300 psi at the rear remote.
I took the hoses off the rear lift cylinders and there is no fluid coming out of the cylinders.

 

[TheOldHokie]

How can I go about seeing if it is bypassing in the steering system?
I am only getting about 1300 psi at the rear remote.
I took the hoses off the rear lift cylinders and there is no fluid coming out of the cylinders.

The PS has its own pump and is a different circuit.

I will have to do a little research on the M7040 plumbing to see where to go next.

Dan

 

[TheOldHokie]

The PS has its own pump and is a different circuit.

I will have to do a little research on the M7040 plumbing to see where to go next.

Dan

There arent many places to use as test points in that plumbing.

Kubota wants you to use a "special tool" (adapter block) to connect a flow meter to the outlet flange on the pump.

There is also a joint in the delivery pipe that looks like you could hook up there with a simple hydraulic fitting. That would be my first choice.

In either case if you dont happen to own a high dollar flow meter you also need to construct a pressure test rig from some hose, a needle valve and a pressure gauge. Pretty simple. You up for that much work?

Dan

 

[Mikec575]

There arent many places to use as test points in that plumbing.

Kubota wants you to use a "special tool" (adapter block) to connect a flow meter to the outlet flange on the pump.

There is also a joint in the delivery pipe that looks like you could hook up there with a simple hydraulic fitting. That would be my first choice.

In either case if you dont happen to own a high dollar flow meter you also need to construct a pressure test rig from some hose, a needle valve and a pressure gauge. Pretty simple. You up for that much work?

Dan

I am up for the work. It's having the knowledge to do it without deadbeading and damaging the brand new pump.

 

[TheOldHokie]

I am up for the work. It's having the knowledge to do it without deadbeading and damaging the brand new pump.

I did not realize it was a new pump.That changes the troubleshooting calculus...

Dan

 

[Mikec575]

I did not realize it was a new pump.That changes the troubleshooting calculus...

Dan

Sorry I didn't mention that earlier. When I have mentioned about a new pump or part everyone always says you still need to test the pump

 

[TheOldHokie]

Sorry I didn't mention that earlier. When I have mentioned about a new pump or part everyone always says you still need to test the pump

Ask "everyone" what they expect to learn by testing the new pump.

Lets backup a minute.

When you tested pressure at the remote did you test with the oil cold and then again when hot. How do those two numbers compare?

Did you have engine speed up around 2000 RPM when measuring pressure?

Dan

 

[Mikec575]

I only tested it cold.
Yes sir I was around that 2200 rpm when getting that pressure.
also did I mention I swapped the relief valves just to rule that out as well. The 7040 relief valve didn’t seem to increase pressure when trying to adjust it so I just took the 7060 that has good pressure and put it in the 7040 with no change in pressure.
no I did not put the 7040 (low pressure tractor) into the 7060 ( good pressure tractor)

 

[TheOldHokie]

I only tested it cold.
Yes sir I was around that 2200 rpm when getting that pressure.
also did I mention I swapped the relief valves just to rule that out as well. The 7040 relief valve didn’t seem to increase pressure when trying to adjust it so I just took the 7060 that has good pressure and put it in the 7040 with no change in pressure.
no I did not put the 7040 (low pressure tractor) into the 7060 ( good pressure tractor)

No, you did not mention any of that and this is not adding up.

You only had 1300 PSI cold yet you say the lift works fine when the oil is cold. How fo we reconcile that?

I think we need another pressure test with both hot and cold oil before doing anything else. The pressure gauge should be plugged directly into a remote, engine at 2200 RPM, and remote lever moved and held full open for at least 5 seconds.

Dan

 

[lugbolt]

I've had a relief valve in the position control valve assembly) stick and cause this exact same thing. I did 8 or 10 of them before I left the kubota business. On cab models you have to lift the cab a little bit to get the position control valve assembly out. But you need to be able to diagnose it properly so you're not unnecessarily removing parts. Out of those ones I had to do, 100% of them had TSC hydrualic fluid in them. Just saying.