Increasing hydraulic pressure using shims

[kris77]

Hey guys, I have a quick question.

Bx2370

I felt like my loader was struggling to lift and dig after about 5-6 yrs of owning the tractor. I ordered the Bxpanded shim/gauge kit and tested my pressure and it was at 1500psi. I took out the PRV and added a .3 shim and tested again and the pressure increased to 3000psi. I didnt think that was right and maybe some dirt or something got on the shim so I took it back out and removed the shim and the shim that was in there from the factory. Now it's sitting at 2600psi with no shims at all.

This makes no sense to me whatsoever. Anyone seen anything like this or have any advice for me? I was trying to get it set at around 2000psi, but i'm not sure what went wrong.

 

[MOOTS]

Pressure can be changed just by tightening that big nut. Did the same on my MX. Bought a few shims and a gauge. Tested, tightened the nut a bit and have been happy.

 

[DustyRusty]

Don't know what the maximum that the factory specifies, but I think that 2600 is enough for the BX to make a great difference in lifting. Just make sure that you have sufficient ballast on the rear so you don't get into trouble.

 

[TheOldHokie]

Hey guys, I have a quick question.

Bx2370

I felt like my loader was struggling to lift and dig after about 5-6 yrs of owning the tractor. I ordered the Bxpanded shim/gauge kit and tested my pressure and it was at 1500psi. I took out the PRV and added a .3 shim and tested again and the pressure increased to 3000psi. I didnt think that was right and maybe some dirt or something got on the shim so I took it back out and removed the shim and the shim that was in there from the factory. Now it's sitting at 2600psi with no shims at all.

This makes no sense to me whatsoever. Anyone seen anything like this or have any advice for me? I was trying to get it set at around 2000psi, but i'm not sure what went wrong.

What Matt said plus the relief valve may not have been sealing properly and when you disassembled and cleaned it you fixed that problem. 2600 PSI sounds pretty high to me - what is the Kubota specification on the loader?

Dan

 

[imnukensc]

Should've indexed the bolt before removing it. Pressure can be increased just by overtightening the bolt.

 

[Mark_BX25D]

I'd be skeptical of those readings, but they are very high. IIRC, the upper limit is 2,000 psi for the BX series.

 

[kris77]

I read on another forum that the seat behind the spring can be pushed in a big too far. Looking back, maybe I overtightened it and pushed the seat in farther than it should be? Is that possible?

I did miss a shim that was stuck in the end of the cap earlier. I have removed all shims now and got the pressure down to about 2300. That's still a little high for my liking but it's way better than 2600-3000 that it was.

When I remove the PRV, and look in the hole at the seat, does anyone know what it should look like? Maybe I did overtighten on the initial shim install??

 

[leveraddict]

Overtightening the relief valve will increase pressure! I went through the same thing with my BX and the shim kit. I posted the problem here looking for how tight (psi) the relief valve should be tightened but got no response! Since the bx should be around 1850 IIRC most only boost to 2000! Its your machine I wont tell you what to do but thats a bit high! You could loosen it a bit and recheck your pressure!

 

[mikester]

Putting lipstick on a pig won't make it a princess.

If you need to lift 3,000 lbs (or more than 800lbs on your machine) get a forklift/SS/CTL or a much bigger CUT. A SCUT isn't made for lifting, it's made for mowing your lawn and moving mulch in your garden.

 

[lugbolt]

were ya testing with the engine RPM at maximum? If not, you should be.

 

[kris77]

I don't really need to lift alot, after a few years I noticed my loader wasn't as strong as I thought it was. Decided to test the pressure. And like I expected, I was a bit low at 1500psi. So I tried to shim it a bit to bump it to 2000psi. But I really think I overtightened the bolt the first time and pressed the seat in farther than it should be. I've read a few others have done the same thing. I just don't know how to verify that.

One mechanic told me to take the PRV out, remove the spring, reinstall the bolt and use the loader function. The increase in pressure would push the seat back to normal position. But I have no idea if that is the right thing to try or not. After removing all shims, I'm sitting at 2300psi. I've seen guys run like that for years and be fine, but that's a little high for my liking. I would like it closer to 2000psi.

Still doing some reading, but wanted to note what I found here to see if anyone agreed or disagreed with that plan.

 

[BX'r]

I would run it at 2300 and re-test it in a month.
It will decrease over time on its own as the spring weakens.

 

[motionclone]

Putting lipstick on a pig won't make it a princess.

it's made for mowing your lawn and moving mulch in your garden.

Careful, your first statement is no longer "accurate" or politically correct!!

And for your second statement, Did Sidecarflip hack your account?

 

[TheOldHokie]

I don't really need to lift alot, after a few years I noticed my loader wasn't as strong as I thought it was. Decided to test the pressure. And like I expected, I was a bit low at 1500psi. So I tried to shim it a bit to bump it to 2000psi. But I really think I overtightened the bolt the first time and pressed the seat in farther than it should be. I've read a few others have done the same thing. I just don't know how to verify that.

One mechanic told me to take the PRV out, remove the spring, reinstall the bolt and use the loader function. The increase in pressure would push the seat back to normal position. But I have no idea if that is the right thing to try or not. After removing all shims, I'm sitting at 2300psi. I've seen guys run like that for years and be fine, but that's a little high for my liking. I would like it closer to 2000psi.

Still doing some reading, but wanted to note what I found here to see if anyone agreed or disagreed with that plan.

I assume we are talking about the pressure relief in the loader valve?

If so I think the part you are calling the seat is the poppet. The poppet is the movable element that the spring holds against the machined seat which is in the body of the valve.

Dan

 

[kris77]

I assume we are talking about the pressure relief in the loader valve?

If so I think the part you are calling the seat is the poppet. The poppet is the movable element that the spring holds against the machined seat which is in the body of the valve.

Dan

So the movable piece I can see when the bolt and spring is removed is the poppet? What is the "seat" i'm reading about that can get stuck if you over tighten the bolt? I've been trying to find a diagram but have come up short.

Here is one post i'm referring to...Pretty sure I have the same issue as this guy.

The problem was my seat relief valve was stuck. I guess I over tightened the bolt at first, but I don't know. I took out the spring and poppet relief and put the bolt back on. Then, I ran the tractor with full rpms and moved the loader lever to one side. The pressure of the hydraulic fluid moving through seat relief valve pushed it back out. I removed all the shims from the bolt and reinstalled the bolt with spring and poppet relief. The tractor read 2100psi which is exactly what I wanted from the beginning! Was a weird experience and I found out not much people have this issue but I'm happy I figured it out.

 

[TheOldHokie]

So the movable piece I can see when the bolt and spring is removed is the poppet? What is the "seat" i'm reading about that can get stuck if you over tighten the bolt? I've been trying to find a diagram but have come up short.

Here is one post i'm referring to...Pretty sure I have the same issue as this guy.

The problem was my seat relief valve was stuck. I guess I over tightened the bolt at first, but I don't know. I took out the spring and poppet relief and put the bolt back on. Then, I ran the tractor with full rpms and moved the loader lever to one side. The pressure of the hydraulic fluid moving through seat relief valve pushed it back out. I removed all the shims from the bolt and reinstalled the bolt with spring and poppet relief. The tractor read 2100psi which is exactly what I wanted from the beginning! Was a weird experience and I found out not much people have this issue but I'm happy I figured it out.

I don't understand his description either.

In standard valve speak the seat would not move - it is typically a machined surface on the valve casting and is at the very bottom of the hole. The poppet is the moving element that is held against the seat by spring tension and closes the center opening in the seat. Have you removed the piece you can see to look behind it? It's possible the poppet in this valve is two or more pieces that move together and that is what he is describing but without a good parts diagram of the valve we really don't know.

In any event you seem to have something wrong here. Do as he describes - remove the spring and all shims then deadhead the loader valve. Then remove everything you can from the relief cavity. If you have removed all of the parts you should see an opening at the bottom. Then reassemble, test, and shim as needed.

Dan

 

[TheOldHokie]

So the movable piece I can see when the bolt and spring is removed is the poppet? What is the "seat" i'm reading about that can get stuck if you over tighten the bolt? I've been trying to find a diagram but have come up short.

Here is one post i'm referring to...Pretty sure I have the same issue as this guy.

The problem was my seat relief valve was stuck. I guess I over tightened the bolt at first, but I don't know. I took out the spring and poppet relief and put the bolt back on. Then, I ran the tractor with full rpms and moved the loader lever to one side. The pressure of the hydraulic fluid moving through seat relief valve pushed it back out. I removed all the shims from the bolt and reinstalled the bolt with spring and poppet relief. The tractor read 2100psi which is exactly what I wanted from the beginning! Was a weird experience and I found out not much people have this issue but I'm happy I figured it out.

I was curious and downloaded the WSM. The relief valve you are adjusting is in the pump. Here is the parts diagram for it. Item number 90 is the poppet and item number 80 is the seat. The seat does not move - pressure is relieved when oil pressure in the damping chamber on the end of the seat forces the poppet out of the bore in the seat and oil flows past the poppet to tank. The spring is the biasing element that sets the poppet cracking pressure. I can see how over tightening the plug might make it difficult to get the seat out but I do not see how that will cause any change in poppet cracking pressure

Dan

 

[kris77]

Thank you for this. When I remove the spring, I do see the poppet. It moves. It kind of is floating in there. If I try and pull the poppet out just a bit, fluid flows out from behind it. Not real sure what happened when I tightened the plug down.

 

[TheOldHokie]

Thank you for this. When I remove the spring, I do see the poppet. It moves. It kind of is floating in there. If I try and pull the poppet out just a bit, fluid flows out from behind it. Not real sure what happened when I tightened the plug down.

If the poppet is not frozen and you have removed ALL of the shims pressure should be no more than factory specification. Flush that plug out good to make sure you don't have shims stuck inside it. The parts diagram also shows two plain washers inside the plug. Here is another cross section of the valve from the WSM.

Dan