M4900 Hydraulic Problems. Power steering, PTO are OK. Everything else weak

[wheelinag]

I bought a M4900 in January of this year with 593 hours on it. At 600 hours, I changed all fluids and filters. Everything has been working great. I ran an auger with an adjustable top link for over 500 holes and my brush hog also uses the remote. FEL has being working well. Tractor now has 643 hours.

Today I'm mowing 16 acres and at the very end I notice that I can't lift the mower any more using the remote. That prompted me to check the loader, which the lift didn't work and the curl barely works. I checked the fluid and it was a little low. Filled it up and no change.

3 point arms immediately drop when I shut it off. If I rev up to 2300RPM's I can get the loader to barely move up. The remote won't pick up the mower, but I can see the hydraulic line move like it's getting a little pressure.

I researched a little bit and figured out there are "two hydraulic systems", but not sure how that works yet. Steering and PTO work fine, I know those are on the priority system. From diagrams it looks like the flow goes from the pump into the 3 point case, but I haven't gotten any further than that. I also check the 3 point control linkage and everything is connected. I also tried many positions of the 3 point resulting in no change.

Suggestions? Where do these systems split the primary vs secondary parts?

Thanks in advance.

 

[North Idaho Wolfman]

PTO is Not hydraulic, it's mechanical.
PTO = Power take off, (spinning shaft) not the three point lift.

It's very possible the three point lever / feedback are mal adjusted and causing the system to go into relief.
You need to set the three point in a middle position and see if that helps.

If it does then get the WSM (aka service manual) and adjust the feedback linkage.

 

[wheelinag]

PTO is Not hydraulic, it's mechanical.
PTO = Power take off, (spinning shaft) not the three point lift.

It's very possible the three point lever / feedback are mal adjusted and causing the system to go into relief.
You need to set the three point in a middle position and see if that helps.

If it does then get the WSM (aka service manual) and adjust the feedback linkage.

PTO is Not hydraulic, it's mechanical.
PTO = Power take off, (spinning shaft) not the three point lift.

It's very possible the three point lever / feedback are mal adjusted and causing the system to go into relief.
You need to set the three point in a middle position and see if that helps.

If it does then get the WSM (aka service manual) and adjust the feedback linkage.

I saw someone else referencing their PTO on the same model. That's the o ly reason I mentioned it.

Position of 3 point has no effect on the problem.

I can hear a change in pump noise when I try to move the loader.

 

[North Idaho Wolfman]

Which exact model do you have, if you don't know give me the serial number.

 

[North Idaho Wolfman]

Loader model number too please.

 

[wheelinag]

Loader model number too please.

M4900 utility special. On the frame M490-50976.

Loader is LA1002

Thanks for your help

 

[woodman55]

I don't think the linkage out of adjustment is the issue, because this happened suddenly. It may be disconnected or broken, but the O P stated it all looks good.

 

[North Idaho Wolfman]

There is a selector valve and if that is in the wrong position the loader and the remotes will quit working but the three point and steering will not be affected.
It would be rather odd if it moved suddenly.

Are there any Quick Disconnects on the loader lines that feed the loader valve?
Does the loader valve move in every direction normally?
Does it have a third function valve?
Does it have more then one remote on the rear?

Are you sure the feed back linkage is intact?

 

[wheelinag]

There is a selector valve and if that is in the wrong position the loader and the remotes will quit working but the three point and steering will not be affected.

Steering is fine.

Any harm in using the tractor as is? I just want to finish mowing and can then bring it home with me.

 

[North Idaho Wolfman]

Steering is fine.

Any harm in using the tractor as is? I just want to finish mowing and can then bring it home with me.

Yes you could do damage to the pump if the unit is going into bypass.

 

[North Idaho Wolfman]

Reread the above post (#8) as I added more info.

 

[North Idaho Wolfman]

Does the mower use a single hose line or dual hose lines to control the cylinder on it?

 

[wheelinag]

Yes you could do damage to the pump if the unit is going into bypass.

 

[wheelinag]

Selector valve is vertical as shown in your diagram.

No 3rd function. Loader valve "feels" normal in all positions. Unsure about the other questions. I'll post pictures of the valve.

Only one set of remotes. Mower only uses one port.

3pt control looks good to me.

 

[North Idaho Wolfman]

Only one set of remotes. Mower only uses one port.

BINGO!
There is the answer that I was looking for.

So what's probably happening is the remote valve is dead heading because of pressure on the other port of the valve.
Most valves do not like only using one side of the valve, it make them stick in an active position.
This will cause all your issues.

The simple solution is to change the cylinder to a 2 way cylinder or add a tank drain to the other port of the remote that you will hook up when you use the mower.

 

[TheOldHokie]

Suggestions? Where do these systems split the primary vs secondary parts?

Thanks in advance.

There is no split. The tractor has a tandem pump. One section is used for PS and the other for loader, remotes and 3pt. Sounds like something is blocking the implement circuit. Make sure your remotes are all in neutral.

Dan

 

[BAP]

Are you making sure that your hydraulic remote control lever is returning to neutral position after raising or lowering your mower? With single hose cylinders, you have to make sure that the lever goes into neutral position after using because most times they won’t automatically. Single hose cylinders work fine, there is hundreds of thousands of mowers and planters in use with them, you just have to pay attention more when using them.