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

[wheelinag]

Frankly I think he has a relief valve problem. He already knows ithe pump produces good volume. About an hour to fabricate a pressure test adapter and test the pump in situ. Unlike a visual inspection the result will be definitive.

Dam

I'm definitely doing a pressure check before doing anything with the pump.

 

[wheelinag]

I'm definitely doing a pressure check before doing anything with the pump.

Well crap. Made an adapter, hooked it up, needle valve all the way open, start tractor, keep closing needle valve. Crap, needle valve is completely closed and gauge only reading 750psi at 2300 RPM's.

Going to check intake side for leaks but other than that, I guess it's the pump? The local hydraulic shop says they have a guy that specializes in rebuilding these guys. I guess I'll get a price.

Edit: these Chinese pumps are tempting, I'm assuming garbage.

Edit 2: I still don't understand how the pump shit the bed that fast.

 

[wheelinag]

Super tempting. Even if it's just to get me through the rebuild?

https://www.amazon.com/OCTOT-3A231-82200-3A23182200-M4900DT-CAB-M5700DT-CAB/dp/B0CZ3C7317

 

[TheOldHokie]

Super tempting. Even if it's just to get me through the rebuild?

https://www.amazon.com/OCTOT-3A231-82200-3A23182200-M4900DT-CAB-M5700DT-CAB/dp/B0CZ3C7317

Thats pretty definitive. Buy the mew pump and 86 the rebuild idea. The new pump will outlast you.

Dan

 

[wheelinag]

The new pump will outlast you.

I'm only 45!

Still want to know what killed this pump that quickly.

Also, I assume all of these Chinese pumps are the same manufacture? I only chose that Amazon link based on speed.

 

[wheelinag]

By the way, I want to thank everyone that's helped. I love fixing my own crap, the troubleshooting process, etc... These kind of forums and the people on them, help with the confidence part of tearing into something new. If anyone ever comes through La Grange, TX the beers on me.

 

[TheOldHokie]

I'm only 45!

Still want to know what killed this pump that quickly.

Also, I assume all of these Chinese pumps are the same manufacture? I only chose that Amazon link based on speed.

I imagine there are multiple manufacturers and even more resellers. Gear pumps are easy for a small CNC shop to crank out.

I have sold dozens of "chinese" pumps with zero comebacks. If that one doesnt outlive you it will be close.

I think I would revisit that flow test before doing anything just to verify it is still pumping. Like you I dont like the sudden failure.

Dan

 

[TheOldHokie]

I'm only 45!

Still want to know what killed this pump that quickly.

Also, I assume all of these Chinese pumps are the same manufacture? I only chose that Amazon link based on speed.

Pardon Our Interruption...

 

[wheelinag]

Pardon Our Interruption...

That's not for a M4900/5700. I almost got fooled too.

 

[North Idaho Wolfman]

Frankly I think he has a relief valve problem. He already knows ithe pump produces good volume. About an hour to fabricate a pressure test adapter and test the pump in situ. Unlike a visual inspection the result will be definitive.

Dam

Both of the below statements tell me to check the pump drive!

I heard a noise and the gauge shot up to 1300 psi. I was at about 1800rpms. 3 point is now not working.
I shut it off and then started it back up again and now I have under 700psi again.

The sound came from the front. I'm assuming the pump area since the pressure line isn't hooked to the loader.

 

[North Idaho Wolfman]

Pull the Pump drive while looking into this issue.
I've seen drive gears internal splines stripped

 

[TheOldHokie]

Pull the Pump drive while looking into this issue.
I've seen drive gears internal splines stripped

View attachment 155171

I suppose anything is possible but I am strugglung to reconcile that with a PS pump that still works. In any event easy enogh to check.

Dan

 

[North Idaho Wolfman]

I suppose anything is possible but I am strugglung to reconcile that with a PS pump that still works. In any event easy enogh to check.

Dan

I agree as it doesn't make sense.

 

[woodman55]

Could the drive gear in that section of the pump be slipping on it's shaft ? That would allow the steering section to function normally. It may have sheared it's key, but still have enough grip to pump up to that lower pressure. That would also explain the momentary jump in pressure.

 

[TheOldHokie]

Could the drive gear in that section of the pump be slipping on it's shaft ? That would allow the steering section to function normally. It may have sheared it's key, but still have enough grip to pump up to that lower pressure. That would also explain the momentary jump in pressure.

The shafts and gears are machined as one piece.

Dan

 

[wheelinag]

I'll definitely check everything in the pump once I get them swapped. I just want to get the tractor back together and working again. I've got to be able to fight this Johnson Grass before it swallows my Pecan trees again!

 

[TheOldHokie]

I'll definitely check everything in the pump once I get them swapped. I just want to get the tractor back together and working again.

I hope a new pump fixes your problem. I also look forward to hearing/seeing the results of the autopsy on the old pump.

While you are at it please consider adding a tank return line to your remote valve setup.

Dan

 

[wheelinag]

While you are at it please consider adding a tank return line to your remote valve setup.

Can you elaborate more? The rear remote? I want to add a second remote, but OEM isn't offered anymore.

I also need to add a 3rd function for a grapple, as limb cleanup will be an ever increasing chore. Right now, I only have to deal with the large native pecan trees in the river bottom. In the future, there will be 35 more acres of trees to deal with.

For the 3rd function, I was looking at getting an entirely new valve block, instead of a solenoid add on style.

 

[TheOldHokie]

Can you elaborate more? The rear remote? I want to add a second remote, but OEM isn't offered anymore.

I also need to add a 3rd function for a grapple, as limb cleanup will be an ever increasing chore. Right now, I only have to deal with the large native pecan trees in the river bottom. In the future, there will be 35 more acres of trees to deal with.

For the 3rd function, I was looking at getting an entirely new valve block, instead of a solenoid add on style.

You are using your double acting rear remote to operate a single acting cylinder. With just one outlet connected the unused outlet deadheads the hydraulic circuit at max system pressure when you retract the SA cylinder. I can't help but wonder if that contributed to your sudden hydraulic failure.

Adding additional rear remotes using a generic directional control valve is damn near trivial. A solenoid operated 3rd function is gemerally favored.

Dan

 

[wheelinag]

You are using your double acting rear remote to operate a single acting cylinder. With just one outlet connected the unused outlet deadheads the hydraulic circuit at max system pressure when you retract the SA cylinder. I can't help but wonder if that contributed to your sudden hydraulic failure.

Adding additional rear remotes using a generic directional control valve is damn near trivial.

Dan

I bought the tractor with that mower from the original owner. I'm pretty sure most of the hours on the tractor were from mowing, so it's definitely not a new addition.

At some point soon, I need to rebuild the cylinder on the mower as it's leaking when it maxes out. I'll add a return line to the other side, as I believe the cylinder is actually a 2 way with a breather installed.