Hydraulic Relief Valve Adjustment

[trynfixit]

Hello, First time here. Looks interesting and helpful.

I have a B3000 I have added hydraulic outlets to. Everything works great, except, the rear hydraulic outlet leaks. Messicks guy was very helpful but I thot I'd try this rather than call him back. I need to lower the hydraulic pressure slightly as it is slightly over what the outlet is rated for. Looking at page 7-M13 in the WSM it looks like I might remove one shim (#8) but it does not say anything about it. I don't know how much that would lower the pressure. Anyone out there familiar with this and know if that's how to do it? Much obliged!

 

[Kennyd4110]

Do you have a gauge setup? If not, this is the first thing you need to get and test the pressure.

 

[Russell King]

What specifically is leaking? If it is a quick coupling then you could just repair or replace the coupling?

 

[trynfixit]

What specifically is leaking? If it is a quick coupling then you could just repair or replace the coupling?

Thanks for reply! No, it's the O rings on the Rear Hydraulic Outlet (RHO) that leak. It's the part (pn 6C040-3925-0) added to provide a pressure and tank port for a remote valve. Mounts to the side of the transmission with two bolts. RHO instructions say 1920 to 1992 psi but the tractor pressure measures 2250 psi. I need to reduce the pressure by adjusting the Pressure Relief Valve by about 260psi. I think you remove one or more of 3 shims but I have no info on which to remove. Trial and error means installing and removing and reinstalling the outlet until I get it right. If I knew how many or which shim to remove could save a lot of repeat. There is a 0.40mm, a 0.20mm, and a 0.10mm shim. I don't know if all three are already in and you remove one or more or which one(s) to remove to reduce pressure enough so it won't leak. Hope that makes sense. Thanks.

 

[PoTreeBoy]

Thanks for reply! No, it's the O rings on the Rear Hydraulic Outlet (RHO) that leak. It's the part (pn 6C040-3925-0) added to provide a pressure and tank port for a remote valve. Mounts to the side of the transmission with two bolts. RHO instructions say 1920 to 1992 psi but the tractor pressure measures 2250 psi. I need to reduce the pressure by adjusting the Pressure Relief Valve by about 260psi. I think you remove one or more of 3 shims but I have no info on which to remove. Trial and error means installing and removing and reinstalling the outlet until I get it right. If I knew how many or which shim to remove could save a lot of repeat. There is a 0.40mm, a 0.20mm, and a 0.10mm shim. I don't know if all three are already in and you remove one or more or which one(s) to remove to reduce pressure enough so it won't leak. Hope that makes sense. Thanks.

I think some of the WSM's told how much a given shim thickness changed the set pressure. I'm pretty sure you could remove 0.40 mm. But most guys are wanting to raise the pressure, not lower it. In any case, I don't think that's the cause of your leak. When you take it apart, check for any burrs or scratches on the mating and seal surfaces and use new o-rings, checking for any defects. Look carefully for a crack or pit in the weld/braze joints on that connector.

 

[trynfixit]

I think some of the WSM's told how much a given shim thickness changed the set pressure. I'm pretty sure you could remove 0.40 mm. But most guys are wanting to raise the pressure, not lower it. In any case, I don't think that's the cause of your leak. When you take it apart, check for any burrs or scratches on the mating and seal surfaces and use new o-rings, checking for any defects. Look carefully for a crack or pit in the weld/braze joints on that connector.

Thank you again for reply! I'm not getting notifications so just now saw your reply. Thanks for advice and ivwill look further for shim specs in my WSM. I'd rather not lower the pressure, would only do so because the guy at Messicks said that was likely the cause. Seems strange to me it's not made to take the pressure of the tractor it's designed for. I've used new kubota O rings evey time, have one set left. Although, at least, the last set removed do not show any damage. I am checking the casting and the machined block for any uneveness, have to get some Dykem Blue to complete the test, hopefully today. The machined block itself, the brazed tubing etc and fittings have no leaks. I did find what i consider imperfect machining on the tranny but not by much. Cleaned it up with fine emery but still leaked a little. The oil comes out from behind the block so the o rings are not holding, or, they are not perfectly lined up. There's slop in the holes for the bolts, which the messecks tech said are to allow for expansion when under pressure. I doubt it expands anywhere near the hole oversize. I asked if there is a chance the slop allows the o rings to not perfectly line up with the ports. He assured me that's not a problem. I am going to try to measure whether that is true. Also intend to try to get the o rings centered on the ports. It behaves to me like the o rings are just a tiny bit off the edge of the port so when the pressure is maxed and relief valve bypasses then at that pressure it leaks just a little. If I just start and run the tractor it does not seem to leak. I'm going to try to get it lined up perfectly somehow and try that before lowering pressure. It's so hard to get in there I have just put it on wherever it rests on the bolts. Messicks claimed that was fine but they are really small ports and o rings and quite a bit oversized bolt holes. Several thousandths over. If I learned anything from micrometer measurements I'll post it here. Anyway, thanks again for advice!

 

[TheOldHokie]

Thank you again for reply! I'm not getting notifications so just now saw your reply. Thanks for advice and ivwill look further for shim specs in my WSM. I'd rather not lower the pressure, would only do so because the guy at Messicks said that was likely the cause. Seems strange to me it's not made to take the pressure of the tractor it's designed for. I've used new kubota O rings evey time, have one set left. Although, at least, the last set removed do not show any damage. I am checking the casting and the machined block for any uneveness, have to get some Dykem Blue to complete the test, hopefully today. The machined block itself, the brazed tubing etc and fittings have no leaks. I did find what i consider imperfect machining on the tranny but not by much. Cleaned it up with fine emery but still leaked a little. The oil comes out from behind the block so the o rings are not holding, or, they are not perfectly lined up. There's slop in the holes for the bolts, which the messecks tech said are to allow for expansion when under pressure. I doubt it expands anywhere near the hole oversize. I asked if there is a chance the slop allows the o rings to not perfectly line up with the ports. He assured me that's not a problem. I am going to try to measure whether that is true. Also intend to try to get the o rings centered on the ports. It behaves to me like the o rings are just a tiny bit off the edge of the port so when the pressure is maxed and relief valve bypasses then at that pressure it leaks just a little. If I just start and run the tractor it does not seem to leak. I'm going to try to get it lined up perfectly somehow and try that before lowering pressure. It's so hard to get in there I have just put it on wherever it rests on the bolts. Messicks claimed that was fine but they are really small ports and o rings and quite a bit oversized bolt holes. Several thousandths over. If I learned anything from micrometer measurements I'll post it here. Anyway, thanks again for advice!

I think someone is blowing smoke up your nether parts. Those orings should hold a lot more pressure than 2000 PSI.

I would absolutely not lower the system pressure. Something is wrong with the seal between the outlet block and the case. Bad orings, wrong size orings, and/or bad surface prep.

The bolt holes are going to be a good bit oversize by design. Typical clearance fit on bolt holes is something like 1/64 = .016

Dan

 

[DaveFromMi]

There should be a safety factor that drove the design of the o rings and sealing surfaces. The guy from Messicks is essentially saying that there is little or no margin between top operating pressure and a failure.

 

[trynfixit]

I think someone is blowing smoke up your nether parts. Those orings should hold a lot more pressure than 2000 PSI.

I would absolutely not lower the system pressure. Something is wrong with the seal between the outlet block and the case. Bad orings, wrong size orings, and/or bad surface prep.

The bolt holes are going to be a good bit oversize by design. Typical clearance fit on bolt holes is something like 1/64 = .016

Dan

Thank you! O rings are OEM same in that came with the outlet kit. Using new ones each time I do it over. 4th time coming up. It goes together easily. Am going to check the casting yet. Have checked the outlet block, seems to have no imperfections. I intend to hold off on lowering the pressure as I don't want to do that unless there is no other way. The spec on the "Rear Hydraulin Outlet" installation instructions is about 260 psi less than the tractor spec. I don't know why they would do that. Seems unkabota design. Tho I'm new to kubota. Anyway thanks!

 

[trynfixit]

There should be a safety factor that drove the design of the o rings and sealing surfaces. The guy from Messicks is essentially saying that there is little or no margin between top operating pressure and a failure.

Right, which seems odd to me. Seems the block should be designed for the tractor it is for. Thanks.

 

[PoTreeBoy]

I suspect some residue from the original cover seal. It only takes a wee bit, and that looks like a tough place to access.

 

[TheOldHokie]

Right, which seems odd to me. Seems the block should be designed for the tractor it is for. Thanks.

Where are you getting a specification for the outlet block? That seems like an exceedingly odd piece of data. I think you are misinterpreting that.

The original blank cover uses the same type of o-ring face seal. It held pressure and did not leak. Its not the amount of hydraulic pressure - its the seal on the new cover. Either the parts or bad or there is something wrong in the installation.

Is this a complete OEM valve kit with pressure out, pressure return, and tank return ports? Post a picture of that block.

Dan

 

[TheOldHokie]

Right, which seems odd to me. Seems the block should be designed for the tractor it is for. Thanks.

Here is your block.

According to Messicks it fits 47 very different models. i am quite sure the number in your instructuons is not the maximum pressure rating of the block itself. Its probably the system pressure of one of those dufferent models chosen at random by some clueless document author.

So back to your problem. Are you positive its leaking at the orings?

Dan

 

[trynfixit]

Do you have a gauge setup? If not, this is the first thing you need to get and test the pressure.

Yes, that's how I know the pressure. Thanks.

 

[trynfixit]

Where are you getting a specification for the outlet block? That seems like an exceedingly odd piece of data. I think you are misinterpreting that.

The original blank cover uses the same type of o-ring face seal. It held pressure and did not leak. Its not the amount of hydraulic pressure - its the seal on the new cover. Either the parts or bad or there is something wrong in the installation.

Is this a complete OEM valve kit with pressure out, pressure return, and tank return ports? Post a picture of that block.

Dan

The Block and all related parts are OEM, the valve is not. Valve has P and T ports. Also has PB but not using that. The entire assembly works great, 3 remotes on rear and two on front. Only thing is the Block leaks a little at end of stroke when goes to the PRV.
Spec is on the attached OEM Instruction Manual. Says 1920 to 1992 psi. Tractor PRV is at 2250 psi, which is in range for the tractor. Block with O rings also attached. I put in new OEM O rings each time though they do not look damaged. Thanks.

 

[TheOldHokie]

The Block and all related parts are OEM, the valve is not. Valve has P and T ports. Also has PB but not using that. The entire assembly works great, 3 remotes on rear and two on front. Only thing is the Block leaks a little at end of stroke when goes to the PRV.
Spec is on the attached OEM Instruction Manual. Says 1920 to 1992 psi. Tractor PRV is at 2250 psi, which is in range for the tractor. Block with O rings also attached. I put in new OEM O rings each time though they do not look damaged. Thanks.

The two ports in that block are pressure out and power beyond high pressure return. The tank return port is the unused port in the transmission case.

You are using tje tank return port on your valve for power beyond. Thats probably about 1500 PSI more than its rated for and I suspect the manufacturer would not approve.

Back to your problem and its not the system pressure.

The OD of the orings should be a little larger than the ID of the ports in the block (snug fit) and when fully seated they should protrude above the surface. Check and measure that protrusion with a straight edge.

Dan

 

[trynfixit]

The two ports in that block are pressure out and power beyond return. The tank return port is the unused port in the transmission case.

You are using tje tankbreturn port on your valve for power beyond. I suspect the manufacturer would not approve.

Back to your priblem and its not the system pressure. The OD of the orings should be a little larger than the ID of the ports in the block and they should protrude above the surface. Check that protrusion with a straight edge.

Dan

Thanks for info! I did use the PB port, longer story, but did not work. Bought the valve from Summit H, they said to use the tank port and disconnect the PB, which I did and it works great as far as operation is concerned. The O rings do protrude above the block. I believe they are a little larger than the port. Not much. Thanks!

 

[TheOldHokie]

Thanks for info! I did use the PB port, longer story, but did not work. Bought the valve from Summit H, they said to use the tank port and disconnect the PB, which I did and it works great as far as operation is concerned. The O rings do protrude above the block. I believe they are a little larger than the port. Not much. Thanks!

Using power beyond is the proper way to connect that valve and it will work perfectly if correctly plumbed.

If Summit told you to use the tank port they did not understand your situation. You probably told them the port on the tractor is a return to tank which it is not. It is high pressure carry over (power beyond) for the 3pt and will see full system pressure. The tank port on Summit's valve is rated for a maximum of 725 PSI.

None of that has anything to do with your leak problem.

Dan

 

[trynfixit]

The two ports in that block are pressure out and power beyond high pressure return. The tank return port is the unused port in the transmission case.

You are using tje tank return port on your valve for power beyond. Thats probably about 1500 PSI more than its rated for and I suspect the manufacturer would not approve.

Back to your problem and its not the system pressure.

The OD of the orings should be a little larger than the ID of the ports in the block (snug fit) and when fully seated they should protrude above the surface. Check and measure that protrusion with a straight edge.

Dan

If I understand correctly it sounds like I should move my tank port hose to the PB outlet on the valve. Does the valve then operate as it does now only the PB port is made for the pressure? The RHO Insructions do not say the "Inlet" is a PB port, only that it is the "Inlet" from the implement, (see photo attached to another reply). I originally thought the PB port was to be tee'd into the PB line from the FEL, per kubota instructions I found online. But I didn't really understand. I did that but it did not work. That is when Summit said go from tank port to return (Inlet) on R H Outlet Block. It worked correctly. Now that I think about it perhaps I could saved trouble by going from FEL PB line to the valve P port and then from PB port on valve back to PB port on the tranny. Skip this $200 Rear Hydraulic Outlet Block altogether. Lot of work and expense. I'd want to know that is best b4 doing it. This does work great, just leaks a little. Thanks for advice and thots!

 

[TheOldHokie]

If I understand correctly it sounds like I should move my tank port hose to the PB outlet on the valve. Does the valve then operate as it does now only the PB port is made for the pressure? The RHO Insructions do not say the "Inlet" is a PB port, only that it is the "Inlet" from the implement, (see photo attached to another reply). I originally thought the PB port was to be tee'd into the PB line from the FEL, per kubota instructions I found online. But I didn't really understand. I did that but it did not work. That is when Summit said go from tank port to return (Inlet) on R H Outlet Block. It worked correctly. Now that I think about it perhaps I could saved trouble by going from FEL PB line to the valve P port and then from PB port on valve back to PB port on the tranny. Skip this $200 Rear Hydraulic Outlet Block altogether. Lot of work and expense. I'd want to know that is best b4 doing it. This does work great, just leaks a little. Thanks for advice and thots!

Had ypu asked I would have told you to daisy chain off the loader valve. Its more accessible and less expensive.

To properly plumb your valve you would need to first install the power beyond sleeve in the N port. Then connect that sleeve to the inlet port on the hydraulic outlet block. You must also connect the T port on the valve to a direct tank return on the tractor. Without it nothing hooked to your valve will work.

Again none of this is related to the leak. So what do youbwant to fix?

Dan