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

[wheelinag]

Well now I'm even more confused. I took the main relief valve out again, disassembled it, put it back together and in the tractor. Started it back up, still have the gauge hooked to the "in" port hose. Had it running for a couple of minutes while messing with the adjustment of the relief valve, 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.

 

[TheOldHokie]

About 99.9% sure. Here is valve I took out and inspected. And yes, I hooked the gauge directly to the hose.

Not sure where to go from here. Is there another relief valve in the 3pt system? I'm hesitant to mess with the pump because I think I'll just end up with the same result.
d youd youv

Pretty sure you got the right relief valve. How did you go about setting the adjustment screw?

Ideally the next place to go would be a pump discharge pressure test but thats not an easy test to plumb up on that tractor.



Dan

 

[TheOldHokie]

Well now I'm even more confused. I took the main relief valve out again, disassembled it, put it back together and in the tractor. Started it back up, still have the gauge hooked to the "in" port hose. Had it running for a couple of minutes while messing with the adjustment of the relief valve, 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.

Thats encouraging and sounds very much like the relief valve is misbehaving. Three point wont work because your gauge has power beyond blocked.

Try that again. Watch the gauge as you turn the adjuster in. Pressure should increase as the screw is advanced. System setting is 2700 PSI.

Dan

 

[wheelinag]

Thats encouraging and sounds very much like the relief valve is misbehaving. Three point wont work because your gauge has power beyond blocked.

Try that again. Watch the gauge as you turn the adjuster in. Pressure should increase as the screw is advanced. System setting is 2700 PSI.

Dan

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

I can tell when the relief valve is doing something as when I back it all the way out, like to a 100psi, I can hear a change in the engine. When I screw it in a little, which only gets me back up to 500-700 psi, I can hear the engine change again.

It definitely has some volume going through it. Just for curiosity, I took the gauge of the line and put it into a bucket open flow. Probably shot out half a gallon pretty quick.

Are these pumps 4 bolt flanges or something proprietary?

 

[TheOldHokie]

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

I can tell when the relief valve is doing something as when I back it all the way out, like to a 100psi, I can hear a change in the engine. When I screw it in a little, which only gets me back up to 500-700 psi, I can hear the engine change again.

It definitely has some volume going through it. Just for curiosity, I took the gauge of the line and put it into a bucket open flow. Probably shot out half a gallon pretty quick.

Are these pumps 4 bolt flanges or something proprietary?

In the parts diagram pump looks like a 4 bolt flange but whether its standard or not ?????

Damn relief valve is $500 !!!! Before poppimg for that I would do a pump discharge test. Do you know how thats done?

Dan
Dan

 

[wheelinag]

In the parts diagram pump looks like a 4 bolt flange but whether its standard or not ?????

Damn relief valve is $500 !!!! Before poppimg for that I would do a pump discharge test. Do you know how thats done?

Dan

I do not know how to do the discharge test. I'll take a look in the WSM.

 

[TheOldHokie]

The WSM procedure involves a ($$$$) flow meter.

You can accomplish the pressure portion using this test rig:

1. Remove the delivery pipe from the pump and connect an adapter plate.
2. Connect the adapter to a tee with gauge in the middle.leg
3. Put a 3000 PSI needle valve on the third leg of the tee.
4. Run a hose from the needle valve to the hydrauluc filler

Fully open the needle valve and start the tractor. Then slowly close the needle valve while watching the gauge. Pressure will begin to climb as you clise the valvr. Stop closing the valve when you get to 2700 PSI.

Dan

 

[wheelinag]

The WSM procedure involves a ($$$$) flow meter.

You can accomplish the pressure portion using this test rig:

1. Remove the delivery pipe from the pump and connect an adapter plate.
2. Connect the adapter to a tee with gauge in the middle.leg
3. Put a 3000 PSI needle valve on the third leg of the tee.
4. Run a hose from the needle valve to the hydrauluc filler

Fully open the needle valve and start the tractor. Then slowly close the needle valve while watching the gauge. Pressure will begin to climb as you clise the valvr. Stop closing the valve when you get to 2700 PSI.

Dan

Perfect, make sense to me. I think we have all of this at the shop. Will look in the morning. Thanks again for your help.

 

[wheelinag]

Striking out again. I ASSumed the hard tubing coming off the pump into the 3 point case/axle was a JIC fitting, it's not. It has come kind of rubber looking feral. I'm hoping the fitting it goes into is o-ring boss. Trying to confirm that after lunch, before I tear it apart further.

 

[TheOldHokie]

Striking out again. I ASSumed the hard tubing coming off the pump into the 3 point case/axle was a JIC fitting, it's not. It has come kind of rubber looking feral. I'm hoping the fitting it goes into is o-ring boss. Trying to confirm that after lunch, before I tear it apart further.

I knew you were overly optimistic

I think you will find those are metric compression fittings. The case itself MAY be BSPP.

You need a pump adapter plate. Easy to make if you can get the bolt spacing

Dan

 

[wheelinag]

I knew you were overly optimistic

I think you will find those are metric compression fittings. The case itself MAY be BSPP.

You need a pump adapter plate. Easy to make if you can get the bolt spacing

Dan

Adapter plate is no problem for me to make, but I'm too busy to machine something right now. I'm going to go by the hydraulic shop tomorrow. It looks like a BSP with o-ring for a seal.

 

[TheOldHokie]

Adapter plate is no problem for me to make, but I'm too busy to machine something right now. I'm going to go by the hydraulic shop tomorrow. It looks like a BSP with o-ring for a seal. View attachment 154910

So you are thinking a male JIC to female BSPP port adapter? Thats not going to be common.

I think you could make that adapter plate in the time it takes to source the BSPP/JIC fitting

Dan

 

[wheelinag]

I think you could make that adapter plate

I haven't taken the pipes off the top of the pump, but I assume it's going to need an o-ring groove in the plate? If so, I have to order the correct radius cutter for the lathe, or make a model of the part, get it into Fusion 360, then spit a program out for the mill. Then set it all up.

I might end up having to do that anyways, but the local hydraulic shop said they might have something that works.

 

[TheOldHokie]

I haven't taken the pipes off the top of the pump, but I assume it's going to need an o-ring groove in the plate? If so, I have to order the correct radius cutter for the lathe, or make a model of the part, get it into Fusion 360, then spit a program out for the mill. Then set it all up.

I might end up having to do that anyways, but the local hydraulic shop said they might have something that works.

Just use a counterbore for the oring. You dont even need to match the OEM oring if you dont want.

I would do it seat of my pants on my manual mill in ~30 minutes. This does not require great precision. In a pinch you could use a drill press.

Dam

 

[wheelinag]

Just use a counterbore for the oring. You dont even need to match the OEM oring if you dont want.

I would do it seat of my pants on my manual mill in ~30 minutes. This does not require great precision. In a pinch you could use a drill press.

Dam

This is part of my problem. I used to be able to "rig" stuff much better. After getting a mechanical engineering degree, I'm ruined. I want to model everything and machine tight tolerances...

I don't have many counterbores, but I suppose I could find a holesaw that would probably hold an o-ring.

 

[TheOldHokie]

This is part of my problem. I used to be able to "rig" stuff much better. After getting a mechanical engineering degree, I'm ruined. I want to model everything and machine tight tolerances...

I don't have many counterbores, but I suppose I could find a holesaw that would probably hold an o-ring.

Drill and tap test port then counterbore for -113 oring with a 3/4" endmill. I have done many this way. Here's an example.

Dan

 

[wheelinag]

Drill and tap test port then counterbore for -113 oring with a 3/4" endmill. I have done many this way. Here's an example.

I keep forgetting how small this stuff is... I'm used to working on larger hydraulic crap. I don't do it a lot, but every couple of years we build a press or some kind of odd hydraulic machine.

Anyways, yes, I'm thinking like 1.5" O-rings... Your example will obviously work perfect. I'm stilling going to go by the hydraulic shop as I don't have enough correct hoses fittings to make this happen anyway.

Oh, and the pressure line has a union in it right between the loader attachment plate and the engine oil pan. It looks like the same plastic ferrule compression fittings on both sides of the union, so probably won't get me anywhere. I'd have to take the loader off in order to gain wrench access, and that's not happening with the hydraulics the way they are.

Again, thanks for your help. I might not get back to this for a couple of days...

Hydraulic sizes I'm more used too.

 

[McMXi]

Then how do the hundreds of thousands farm tractors with planters and mowers with single action lift cylinders and dual valves work then? We used them for 40+ years without any issues.

The Land Pride RC3712 that I bought last year has three cylinders set up as single acting. Two to raise the wings and one for the center deck. Many folding cutter manufactures such as Land Pride, Woods, IronCraft, Bush Hog etc. use single acting cylinders for the same functions.

The RC3712 only has two hydraulic lines, but perhaps it should have six and be run off two remotes in float (for the wings) and an SCD for the center deck. Given the cost of the cutter, the addition of four 1/4" hydraulic lines with the appropriate fittings is a drop in the bucket, so shame on Kubota/Land Pride if the current arrangement is merely about profits for them and not about what's best for the customer or tractor.

 

[North Idaho Wolfman]

I'm thinking you have a pump issue!

It wouldn't be that hard to pull the pump and confirm everything is fine with it and the drive.

 

[TheOldHokie]

I'm thinking you have a pump issue!

It wouldn't be that hard to pull the pump and confirm everything is fine with it and the drive.

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