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.