CASE 580D backhoe with weak hoe

[booneyboy]

Need some expert advice as to the next steps to diagnose my case 580D backhoe with lack of power in the hoe attachment. I've already got some good advice as to what to rule out on the heavy equipment forum, but at a standstill now. I changed o-rings on the power beyond valve. I've changed out all the hoe spool valve orings and seals. I've replaced the quick disconnects for the hoe attachment. Put new seals and piston packings on the dipper arm cylinder. Pump seems to be fine since it produces plenty of PSI for front bucket and stabilizer arms as indicated below, Per the service manual I ran a series of pressure checks on the system and the data is listed below. Based on the data, does anything jump out at anyone as to what might be the issue? I am fine with performance of the front bucket; just need the higher PSI to dig with the hoe. Backhoe is my brothers and he can't pinpoint just when it started to lack power to dig with, but used to be fine in the past. Thanks in advance.



Pressure gage installed on control block port coming from pump
-curl front bucket to stop achieves 2700 psi (both cylinders are leaking and need to have seals/piston seals replaced)
-lift front bucket to stop 3000 psi
-retract stabilizer arms to stop 3000 psi
-curl hoe bucket to stop 2200 psi
-pull hoe dipper arm in to stop as well as extend it to stop 1700 psi
-lift hoe arm to stop 2400 psi
-swing hoe arm left or right 2400 psi

Pressure gage installed on steering relief valve per service manual test procedure:
-pressure at 200 psi neutral (spec says less than 500 good)
-pull hoe dipper arm in to stop pressure drops to 100 psi (one section in manual says it should show 2800 psi, another section says to perform the next test mentioned )
-Per manual, max out steering to left or right should be 2050-2150, mine reads 1700 psi. With steering maxed out, pull dipper arm in, spec. says 2850-3150, mine reads 2200 psi

Manual states that if I don't achieve the 2050-2150 when maxing out the steering alone, to adjust the pressure on the steering relief valve. Offhand I did not see anything on valve that would let me do this.
Manual states that if I don't achieve the 2850-3150 with steering maxed and dipper arm pulled in then the piston in the steering relief valve may be stuck and to disassemble the assembly and fix. Another section in manual states that if I am not achieving the correct pressures to disassemble the unloader valve.

Front bucket pressures seem good so am ruling out the pump being bad. Back hoe pressures low but dipper arm is lowest and this affects my digging. We had just installed new seals/piston seals on the dipper arm so ruling out bad seals. I also tightened the bypass valve on this individual spool for the dipper 1.5 turns and it had zero affect.

Any ideas for next steps guys? thanks!

 

[cumminstinkerer]

I would lean towards a faulty circuit relief valve on the dipper circuit, but it could still be in the steering relief valve. get the steering pressure up first then move on to the hoe issues, each system plays a role in all the others, steering is priority however so you need it up to snuff fir sure before you can get into other issues

 

[booneyboy]

I would lean towards a faulty circuit relief valve on the dipper circuit, but it could still be in the steering relief valve. get the steering pressure up first then move on to the hoe issues, each system plays a role in all the others, steering is priority however so you need it up to snuff fir sure before you can get into other issues

Thanks, the steering works fine with the "low" pressure. But from the sounds of it that steering relief valve affects the hoe functions so maybe I will tear that off and disassemble it.....eventually I should run out of parts to rule out!

 

[cumminstinkerer]

yes the steering relief plays into all the rest of the hydraulic functions, I dont have a schematic in front of me, and my memory isn't good enough to remember how the system is laid out.

 

[booneyboy]

yes the steering relief plays into all the rest of the hydraulic functions, I dont have a schematic in front of me, and my memory isn't good enough to remember how the system is laid out.

yeah, I have the manual and see how it ties into the rest of the hoe functions.. I did the pressure tests based on the manual. The steering pressure is not to spec. but not super low either...If I don't hear from anyone else on what to do next I may just take out that steering relief valve and tear apart and at least rule that out

 

[cumminstinkerer]

If memory serves me properly, been a few years since I worked on a D but they all work basically the same set main relief first, then set steering, it is a few hundred psi below main, if you have a flowmeter you actually see the flow change when you hit steering relief, I cant remember if a D has the two stage pump or not, been to many years, 08 was the last I really did hardcore stuff on them. is it only the dipper function you are having issues with? If so that really leads me back to circuit relief valve, they are usually a few 100 above main setting I'm sure the manual has specs but without a test jig its hard to test them other than looking at the seals, I've had them blow a hole through the oring and backup ring and do some weird stuff like you are describing.

 

[booneyboy]

If memory serves me properly, been a few years since I worked on a D but they all work basically the same set main relief first, then set steering, it is a few hundred psi below main, if you have a flowmeter you actually see the flow change when you hit steering relief, I cant remember if a D has the two stage pump or not, been to many years, 08 was the last I really did hardcore stuff on them. is it only the dipper function you are having issues with? If so that really leads me back to circuit relief valve, they are usually a few 100 above main setting I'm sure the manual has specs but without a test jig its hard to test them other than looking at the seals, I've had them blow a hole through the oring and backup ring and do some weird stuff like you are describing.

So the dipper is the lowest psi as shown in my test data, (1700) but the other than the stabilizer arms which achieve 3000 psi, all the other hoe pressures are running 2200-2400. I will check my manual but I assume they should also be 3000 like the spec. writeup I mentioned above. The front bucket is hitting the 3000 so the main relief valve is bypassing at that pressure I believe. Since all the hoe functions are not even 2500 I believe I should concentrate on something that affects all of them next.....which correct me if I'm wrong, that would only be the steering relief valve or the unloader valve. Do you know how to adjust the steering relief valve pressure? I don't see the typical cap nut with an Allen screw under it like all the other bypass valves have. thanks

 

[cumminstinkerer]

I'm sorry I really dont remember on the D's its been way to long, I think what you are referring to as the unloader is really called the priority valve, at least it was on the K's and later, if it is not shifting properly it will do weird stuff, I cant remember for sure either but there maybe a seperate relief valve for backhoe functions as well, I wish I had a schematic here and I could be a bit more help, unfortunately the only one I have around is for a phase 3 K and they are way different.

 

[cumminstinkerer]

makes me wish my service manager from case was still with us, he knew them D's like the back of his hand, I could have relayed to him what you got going and he'd have solved already, if you have a schematic of the hydraulic system send it to me via PM or shoot me a PM and we can swap email and send it that way. I worked on some D's and C's but they were getting up there age wise when I was there, the K's were even getting a bit older.

 

[booneyboy]

makes me wish my service manager from case was still with us, he knew them D's like the back of his hand, I could have relayed to him what you got going and he'd have solved already, if you have a schematic of the hydraulic system send it to me via PM or shoot me a PM and we can swap email and send it that way. I worked on some D's and C's but they were getting up there age wise when I was there, the K's were even getting a bit older.

Ok, will send some pics. DM...for everyone's info. this is the steering relief valve with the gage plummed in it, and below is the unloader valve

 

[mEl]

This may sound strange but have you checked spool travel on the systems that are down in pressure, I have never experienced it on the Ds but i have definitely seen control handles and linkages with enough wear that the levers are hitting the back and front of their slots on the older 530-580 series and not allowing the spools to full stroke. In the above picture there is a valve with a small cap on it and the pressure is increased by loosening the lock nut and screwing the cartridge in, it is the right hand valve with the small line attached to it.

 

[booneyboy]

This may sound strange but have you checked spool travel on the systems that are down in pressure, I have never experienced it on the Ds but i have definitely seen control handles and linkages with enough wear that the levers are hitting the back and front of their slots on the older 530-580 series and not allowing the spools to full stroke. In the above picture there is a valve with a small cap on it and the pressure is increased by loosening the lock nut and screwing the cartridge in, it is the right hand valve with the small line attached to it.

Thanks for the feedback.. I will check the linkage. I know when I replaced all the spool valve o-rings the pins and lever were not loose at all....at least on the upper portion that I had to remove to get the spools out. Appreciate the comment on the adjustment screw! I didn't think it was one because that pilot line was attached, but when I pulled up the schematic it does show it as one! I will try turning that inward a turn and see what that does before I tear it off. thanks!

 

[booneyboy]

This may sound strange but have you checked spool travel on the systems that are down in pressure, I have never experienced it on the Ds but i have definitely seen control handles and linkages with enough wear that the levers are hitting the back and front of their slots on the older 530-580 series and not allowing the spools to full stroke. In the above picture there is a valve with a small cap on it and the pressure is increased by loosening the lock nut and screwing the cartridge in, it is the right hand valve with the small line attached to it.

This may sound strange but have you checked spool travel on the systems that are down in pressure, I have never experienced it on the Ds but i have definitely seen control handles and linkages with enough wear that the levers are hitting the back and front of their slots on the older 530-580 series and not allowing the spools to full stroke. In the above picture there is a valve with a small cap on it and the pressure is increased by loosening the lock nut and screwing the cartridge in, it is the right hand valve with the small line attached to it.

 

[booneyboy]

This may sound strange but have you checked spool travel on the systems that are down in pressure, I have never experienced it on the Ds but i have definitely seen control handles and linkages with enough wear that the levers are hitting the back and front of their slots on the older 530-580 series and not allowing the spools to full stroke. In the above picture there is a valve with a small cap on it and the pressure is increased by loosening the lock nut and screwing the cartridge in, it is the right hand valve with the small line attached to it.

well, nothing hitting, spools are getting their full travel. Another individual suggested the unloader valve. I may have to look into that to see if that or the steering relief valve could be the issue.. Those are really the last two valves in the system that could be the problem that I haven't dug into.

 

[Brokengun]

So the dipper is the lowest psi as shown in my test data, (1700) but the other than the stabilizer arms which achieve 3000 psi, all the other hoe pressures are running 2200-2400. I will check my manual but I assume they should also be 3000 like the spec. writeup I mentioned above. The front bucket is hitting the 3000 so the main relief valve is bypassing at that pressure I believe. Since all the hoe functions are not even 2500 I believe I should concentrate on something that affects all of them next.....which correct me if I'm wrong, that would only be the steering relief valve or the unloader valve. Do you know how to adjust the steering relief valve pressure? I don't see the typical cap nut with an Allen screw under it like all the other bypass valves have. thanks

IF the loader has 3000 psi and other Hoe pressures are 2200-2400 psi but the Dipper Cylinder is 1700 psi, then the problem is going to be in the spool for the dipper cylinder.

Are there backup rings for the o-rings on the dipper spool circuit ? Is there a pressure relief for that spool ?

There is a possibility the Dipper Spool is worn out and allows pressure to by-pass the spool.

I had this happen to me on a Hoe, to fix it, I had to replace the valve.

This is what I would do if the Hoe was mine; I would go back through that spool and inspect everything and I would change every O-Ring, Back Up Ring, etc......

 

[cumminstinkerer]

IF the loader has 3000 psi and other Hoe pressures are 2200-2400 psi but the Dipper Cylinder is 1700 psi, then the problem is going to be in the spool for the dipper cylinder.

Are there backup rings for the o-rings on the dipper spool circuit ? Is there a pressure relief for that spool ?

There is a possibility the Dipper Spool is worn out and allows pressure to by-pass the spool.

I had this happen to me on a Hoe, to fix it, I had to replace the valve.

This is what I would do if the Hoe was mine; I would go back through that spool and inspect everything and I would change every O-Ring, Back Up Ring, etc......

There are no orings on the spools other than the little dust seals on the outer end of the body, there is a circuit relief for both directions of the dipper function, those valves have orings and backup rings externally that can cause issues, also the relief itself could be going bad, it would be very odd for both directions to go bad at the same time, a worn spool would have do be really bad for the pressure loss to show up with the function dead headed, I am very strongly leaning to a circuit relief valve or a cracked valve body but dang thats pretty rare. Also if the body cracks or gets a pin hole, it will cause any function down stream to act weird, like moving on its own, ask me how I know that one!

 

[mEl]

On very rare occasions I have seen the regeneration piston stuck or a broken spring in it. Since all circuits are affected check the regen circuit for problems, if you have a service manual that would be a plus to show you where they are located. there is a regen piston and plunger in the one end section that comes down on an angle and a check valve in the opposite endcap, to check, the regen circuit is designed to shuttle return oil over into the pressure channel when you drop the boom quickly into a ditch when the pump cant supply oil quickly enough to avoid having a void in the oil supply causing a lack of system response, but if it does not close off properly hydraulic flow can go into the return side. A very trouble-free system but can cause you to pull your hair out when everything looks good! Another thought, you have had reliefs out but did you check the check valves under them to see if the rings are gone off the check valve body, A VERY common problem, You need to make a tool for removing them out of a 3/8 bolt grind it till it will slip down in the slot in the check valve then grind it thin enough that it can be put in the slot and turned 90 degrees to use as a tool to lift the checks out. I haven't checked every post so you may have done this already. Those blown O-rings are what cause the systems to interact, for example trying to swing when using another circuit with no swing pedal movement, that is just one possible example.

 

[cumminstinkerer]

\

On very rare occasions I have seen the regeneration piston stuck or a broken spring in it. Since all circuits are affected check the regen circuit for problems, if you have a service manual that would be a plus to show you where they are located. there is a regen piston and plunger in the one end section that comes down on an angle and a check valve in the opposite endcap, to check, the regen circuit is designed to shuttle return oil over into the pressure channel when you drop the boom quickly into a ditch when the pump cant supply oil quickly enough to avoid having a void in the oil supply causing a lack of system response, but if it does not close off properly hydraulic flow can go into the return side. A very trouble-free system but can cause you to pull your hair out when everything looks good! Another thought, you have had reliefs out but did you check the check valves under them to see if the rings are gone off the check valve body, A VERY common problem, You need to make a tool for removing them out of a 3/8 bolt grind it till it will slip down in the slot in the check valve then grind it thin enough that it can be put in the slot and turned 90 degrees to use as a tool to lift the checks out. I haven't checked every post so you may have done this already. Those blown O-rings are what cause the systems to interact, for example trying to swing when using another circuit with no swing pedal movement, that is just one possible example.

Dang you been down this road too, I was hoping to give him the easy stuff first, lol, them regen circuits are unique! I have that very bolt in my custom tool drawer! I have had I believe it was the boom section get a pin hole in the casting and if you dead head whichever one it was it would cause the swing to move or curl the bucket, that was a hair puller, I replaced all the orings between the sections and did the regens too, it did the same crap, I had to pull the thing back out and put sections in the tests fixture and test them with the hand pump, finally found this little casting crude hole that at about 2500 psi would pee a stream right into one of return ports for the swing section. that one was weird. had several with circuit relief valves give issues, only ever had a couple regen valves give trouble, also had one that the one way restrictor for the boom circuit got mushed and wouldn't let the boom go down.

 

[Brokengun]

There are no orings on the spools other than the little dust seals on the outer end of the body, there is a circuit relief for both directions of the dipper function, those valves have orings and backup rings externally that can cause issues, also the relief itself could be going bad, it would be very odd for both directions to go bad at the same time, a worn spool would have do be really bad for the pressure loss to show up with the function dead headed, I am very strongly leaning to a circuit relief valve or a cracked valve body but dang thats pretty rare. Also if the body cracks or gets a pin hole, it will cause any function down stream to act weird, like moving on its own, ask me how I know that one!

I am aware there are NO O rings on the spools that's why I asked; "Are there backup rings for the o-rings on the dipper spool circuit"

This is how I would address this issue if this were my Hoe; I would pull the relief valve on both sides of the dipper cylinder inspect, clean, address any issues and reinstall, then pressure check.

I am not saying this is your problem but I worked on a Hoe that had a worn spool that would pressure and still bleed through enough as to not hold a load. The internal Body of the spool was worn just enough that the internal Edge of the valve Body where the Spool set, allowed it to Bleed threw. I went as far as Measuring the Valve Body with an internal Micrometer and it was within a 1/2 thousandth of the diameter of the spool, but it was just enough to allow for a pressure bleed down issue.
The wear was caused by erosion caused by the normal movement of Hydraulic oil through the spool body.

 

[booneyboy]

I am aware there are NO O rings on the spools that's why I asked; "Are there backup rings for the o-rings on the dipper spool circuit"

This is how I would address this issue if this were my Hoe; I would pull the relief valve on both sides of the dipper cylinder inspect, clean, address any issues and reinstall, then pressure check.

I am not saying this is your problem but I worked on a Hoe that had a worn spool that would pressure and still bleed through enough as to not hold a load. The internal Body of the spool was worn just enough that the internal Edge of the valve Body where the Spool set, allowed it to Bleed threw. I went as far as Measuring the Valve Body with an internal Micrometer and it was within a 1/2 thousandth of the diameter of the spool, but it was just enough to allow for a pressure bleed down issue.
The wear was caused by erosion caused by the normal movement of Hydraulic oil through the spool body.

Thank you for the feedback guys... I had pulled all the spools for the hoe and replaced the dust seals and o-rings (one on top of spool and one at bottom). spools had some minor scuffing but no grooves etc. I did not pull the relief valves for each spool. I will have to do that on the low pressure dipper circuit. I did try adjusting the relief valve by tightening the setscrew a few turns and it had zero affect on the pressure. I do have the service manual; will have to check the Regen you are talking about. I was following the manual pressure test sequence and all was checking out ok (system relief pressure fine, pump fine......) the next two items it was listing as potential issues was the steering relief valve and the unloading valve so those were going to be on my list, but may pull the relief valves on that individual circuit instead.