RK24 Hydraulic failure

[Fergenheimer]

Just joined the community. This post is to both ask and provide information.
I have a problem with my RK24 Hydraulic divider block. There is plug on the bottom side of it which blows out the o-ring seal. This happened to me and since I am out of warranty, I replaced the o-ring and it was "fixed". I had hoped that this was a one-off occurrence. Then it happened again.

Second time, I notice the hydraulic pump changed tone when in a hard right turn. I have not changed the o-ring again. I will but wondering if anybody else has had this problem. I doubt that my problems are unique and if you have seen this I would appreciate hearing about it.

Thanks

 

[agjones]

I suggest posting this in the hydraulics forum for a wider range of eyeballs on the question.

It sounds like excess pressure. You may have a relief valve stuck. You can buy, make or get a shop to use a pressure test gage to verify the spike in pressure.

Could be the result of a collapsed or damaged line or possibly damage to the ps cylinder itself.

The closest relief valve appears to be under the cap nut to the right on the valve body pictured.

If you're out of warranty, TYM built that tractor so their dealer is likely better positioned to help than rk.

 

[Fergenheimer]

Thank You @agjones. Over pressure is what I suspect also. The hydraulic diagram does not show a relief valve. I was going to look at the hydraulic pump for a relief valve next. I will look under the cap first then. I was going to order a gauge and tee to tie it into the pump discharge line. Any idea what pressure should be?
Thanks again for the help.

 

[oldnslo]

Relief valve should be in the first component connected to pressure port of the pump. Do you have a schematic showing what that component is that the seal is failing on?

 

[Fergenheimer]

@oldnslo , it is a divider block. I cannot find a schematic of the internals but the attached are from the parts manual. If I read the schematics right, the steering column drains back to the sump through its own hose. The loader drains back through this divider block.
This time that it failed, I noted a change in sound when I was in a hard right turn. This might be coincidental. First time I saw the leak, I have no idea how long it was leaking. Two other things that are probably coincidental, this occurred shortly after my 50 hour maintenance at the dealer and my wife saw the bucket was holding water and breeding mosquitos. She started the tractor and operated the controls to tilt the bucket. Whether you run the steering cylinder or the bucket cylinders to the end of travel and still hold it, all the oil should return and not build up pressure.

 

[oldnslo]

Is there only one pump on this tractor? By the attachment I would say yes and that block is used to house a priority flow control to provide flow to steering and excess oil to the FEL circuit. Turning to stop will cause pressure to build to relief setting and yes you would hear this same as operating FEL function to end of stroke. The higher pressure would increase chance of seal failure but should not be the root cause.

did you or the dealer ever check to see if pressure settings are to spec?

Was that plug lose when the seal blew?

 

[Fergenheimer]

I have not taken it to the dealer for any troubleshooting. I did show them the pictures above and a video of the block spraying when I operated the loader. They said they had never seen anything like that before. Also did not offer up any additional drawings on that block. The block through RK was $421.58.
I do not recall if the plug was loose. It is on the bottom of the block and mounts on a plate so it cannot back out. When I replaced the o-ring, I did not over torque it since extruding an o-ring is easy to do. Internal to the block beneath this plug, was a ball and spring. Hard to get a good picture. Thought that this might actually be an emergency relief and it is supposed to blow out instead of rupturing something else.

 

[agjones]

I have not taken it to the dealer for any troubleshooting. I did show them the pictures above and a video of the block spraying when I operated the loader. They said they had never seen anything like that before. Also did not offer up any additional drawings on that block. The block through RK was $421.58.
I do not recall if the plug was loose. It is on the bottom of the block and mounts on a plate so it cannot back out. When I replaced the o-ring, I did not over torque it since extruding an o-ring is easy to do. Internal to the block beneath this plug, was a ball and spring. Hard to get a good picture. Thought that this might actually be an emergency relief and it is supposed to blow out instead of rupturing something else.

There are often multiple reliefs in the system. Under that nut is either a relief or an adjustment for the divider.

I think you're on the right track. That lil plug w oring could be a bleeder. It's possible that air was introduced to the system during filter change and pushed out at the oring.

400 is plenty of $for the block but not extreme. Money or time...

The factory cylinders are 2500 and 3000 psi. Typically tractor pressure is around 2300.

 

[Fergenheimer]

Thanks for the info. I just traced out the lines. The return and supply line skirt up under the body and seat area so it is tough to be sure but it looks like the return line is routed to an aux valve on the right column of the ROPS. From there it would return to the sump. Since I generally crawl up on the tractor that way, if I hit the valve and it is not in the neutral position, could that obstruct the return and jack up pressure?

 

[oldnslo]

I have not taken it to the dealer for any troubleshooting. I did show them the pictures above and a video of the block spraying when I operated the loader. They said they had never seen anything like that before. Also did not offer up any additional drawings on that block. The block through RK was $421.58.
I do not recall if the plug was loose. It is on the bottom of the block and mounts on a plate so it cannot back out. When I replaced the o-ring, I did not over torque it since extruding an o-ring is easy to do. Internal to the block beneath this plug, was a ball and spring. Hard to get a good picture. Thought that this might actually be an emergency relief and it is supposed to blow out instead of rupturing something else.

hard to tell what function is on that valve or plug you removed. I do see a small hole between the O-ring and threads so suspect some form of pilot signal or possibly pilot for relief valve. Again this is just a guess.

I presume there was a lead in chamfer for that O-ring and be careful on the torque during installation.
Possibly silly question but how did you size the replacement O-ring. These frequently are not standard hardware store sizes and one to large would cause problems on installation and potentially blow out much easier. Probably a metric seal

 

[Fergenheimer]

Also, looking at the dead grass, the leak started a lot sooner than I realized it. So the blowout was not related to that sharp right turn.

 

[Fergenheimer]

I have an o-ring kit. The o-ring I used had the same id but had a 3mm cross section instead of a 2mm. I did not have the size that was in there.
I had not thought about a pilot line for the relief on that hole. I had guessed it was an orifice to limit flow if you did blow out. I did not get a good shot of the tip of the plug but the attached does show the seat for the ball that I mentioned above. I do not recall a lead in chamfer for the o-ring. I think it was just a flat surface.

 

[oldnslo]

I suspect faulty assembly on first O-ring or cavity plug screws into not machined correctly. Second failure could be similar problem if cavity not correct. That O-ring should fit into a machined chamfer approximately 12 - 15 degree angle. I have seen some where you could see the O-ring chamfer along the hex with the plug installed. If you can see the seal it will eventually blow out.

Wrong size seal can cause same problem since it will not squash into that chamfer and then get trapped between head of plug and body. Smaller the plug the more critical the O-ring size.

 

[oldnslo]

I see You posted 3 mm vs 2 mm cross section that could be a reason second seal failed see my previous post in attempt to explain why

 

[Fergenheimer]

When I get the block off again, I will try and get a picture. The one of the bottom of the block is before I removed the plug and you can see the original o-ring protruding from beneath the plug. Thanks for the help.

 

[Fergenheimer]

As a stop gap until I get a hydraulic test gauge, I'm going to limit my engine speed to 2500 rpm. My assumption is that the hydraulic pump is shaft driven and the faster it turns, the more flow since it is a positive displacement and thus more return flow or more pressure. Is this a good assumption. Full rated pto speed is 3000 rpm. I use a mid mounted pto driven finish mower so it would not be quite as fast.

 

[oldnslo]

Yes flow will increase with engine speed but pressure should have minimal increase from the increase in flow IF the relief valve is sized and working properly.

 

[bbodine90]

Everyone,

I just purchased an Rk24 two weeks ago. I am on my third time replacing this o-ring. Rk is dragging their feet to assist with my warranty. Was a fix ever established for this?

 

[bbodine90]

As a stop gap until I get a hydraulic test gauge, I'm going to limit my engine speed to 2500 rpm. My assumption is that the hydraulic pump is shaft driven and the faster it turns, the more flow since it is a positive displacement and thus more return flow or more pressure. Is this a good assumption. Full rated pto speed is 3000 rpm. I use a mid mounted pto driven finish mower so it would not be quite as fast.

Fergenheimer, have you found a permanent fix for this?

 

[Fergenheimer]

BBodine90, I replied to your message.