TheMethod
New Member
Hello,
Well usually I can fix anything, but this machine has me stumped! So I'm here to beg the Hydraulic Gods to help me diagnose these wandering problems...
Intro: I'm new to heavy iron, we bought this machine to tear down an old house, do some stump and earth clearing, and dig a basement. 590D serial number incoming....
Machine seemed to work fine first 4-5 hours, then started to develop a problem where some functions would not work.. Lets call this failure mode 1.
Failure mode 1: Swing does not work at all (or very slow like an inch every 5 seconds), left propel does not work at all, boom 1/2 speed, arm 1/2 speed, bucket and right propel 100%. When this is happening, I can tease the left propel into working if I press the right propel, left propel, and slightly pull back on the boom handle. (Deere style control pattern) I think when this is happening that I can "hear" fluid or engine sound change slightly when the functions are being activated but not moving, like the fluid is being dumped off somewhere.
Fail 1 is the usual failure I will experience.
Sometimes it will flip to
Failure mode 2: Boom will barely lift itself, only enough to take the slop out of the pins. Right propel dead, arm 1/2 speed, bucket super slow. Swing seems to work, left propel will work.
So I did my own looking around and learned that these functions (failure mode 1) are all related to the rear pump section, and the left control valve side. We called Deere out to have a look. They sat in the truck awhile and read the computer manual about our "super old" machine, ran the machine a bit, and proclaimed that it "needed a new pump" for sure. (in hindsight, I should have been there to question their diagnostic methodology given that they never attached any gauges or flow meter to the machine)
Machine sat like this for awhile as it was super cold and frozen. I removed the pump, sent it off to be rebuilt. I drained all fluid that I could access, including vacuuming out the hydraulic tank, (was very clean) replacing suction filter, screen, pilot filter. Installed new pump, filled oil, primed pump and fired it up. Checked pilot oil pressure with gauge, around 700.
Machine was no change in operation. Seems to run fine for a little while, then all of a sudden the functions go out. When it goes out it is all of a sudden, aggressive stop. Usually will not come back, sometimes if I idle low for awhile it will come back.
So I dug hard into the workshop and diagnostic manuals. I started to suspect the regulator that controls the rear pump stroke control, maybe it is not working correctly and "stroking down" the rear pump to minimum displacement, and that is causing all functions on that pump to stop? When the left propel, right propel are pushed together and you add some boom control it shifts the combination valve and sends some front pump oil to the left propel and it works? I put my gauge on the rear pump regulator line and it seems to show pressure at the 300psi or so when no functions activated, and goes down to 40 psi or so when you are activating functions, but the function is not working. This does not change whether the function is working or not.
I don't suspect that the pilot or spools are not working, because when I stroke one of the "lame" functions, I can look over my shoulder and see the swing brake release line flex. The spools are moving and releasing the swing brake, even if the function is not moving.
So then I wanted to look at the spools, and combination valve. I cleaned the top of the control valve, and removed both spool covers. Combination valve moves nicely, same with the bypass valve next to it. All spools can be pulled up to the top of their bore, then dropped and they will slide right in nicely....
Except for the left propel spool! It was not super loose, in fact I had to twist and pull pretty hard to get it out. It did not want to come out or move nicely in the bore. So it seemed like a smoking gun, but it did not fit the problem that I was having. If it was siezed in the bore and did not move, that function alone would stop working but not affect all the others correct? If it stuck in an "open" position, the track would be stuck turning etc? The spool looked fine, no mars or marks. I micro-polished it anyway with some Crocus cloth. Still would not slide in nicely. Now don't judge me, but I ran an appropriately sized 1000 grit dingleberry hone in the spool bore and cleaned it up so that it would slide in pretty nicely. It hits a tough spot midway through, but once it is all the way seated it will move easily through it's small range of motion. Absolutely no change in operation, failure mode 1.
So I noticed the the arm (stick) would move the wrong way if I was trying to slowly move the arm out, so I started to suspect the circuit relief valve. You can tell that many of these have been replaced, as they are a brown color instead of yellow. I removed the two arm circuit relief valves and swapped them. Now it seemed to switch to failure mode 2! Coincidence? I have studied the hydraulic diagrams, and I cannot make myself see how a bad circuit relief valve could cause my failure mode 1 or 2. If you had a bad circuit relief, that function would be slow/lame in that direction but not kill everything else on the control bank side correct?
So I went to swap them back again and when I pulled one out I noticed the Oring and backup washer were half gone! (this could have been my fault when I swapped it really fast while being showered in oil from above, with my arm blindly shoved up the hole while sitting on a pile of 100 year old house rubble) So I got 2 sets of the rings from Deere this morning (all they had in stock) and put new rings on both of those circuit relief valves. No change, Failure mode 1 after it worked correctly for about 20 minutes. Shut down for awhile, fired back up and worked for a few minutes, then failure mode 2! I did play around with the arm stick while it was working, and it does seems like it will go the wrong way in both directions, it's just harder to see it in the "out" direction because gravity helps. I had to pull the arm all the way back in to see it happening. So this may be caused by a worn cylinder piston seal instead, put that on my list.
So I am getting low on ideas, I just can't think of anything that would cause these failure modes, especially when they change back and forth like that.
I am planning to order more orings and re-seal all the other 6 circuit relief valves.
I plan to disconnect the "aux" function hoses that are currently screwed together and confirm that there is not a huge leak across that circuit. (had a thumb on it previously we think)
I plan to plumb gauges into both pumps to see what the pressure is both when the machine is working, and when it goes into failure. (I probably should have done this first) One thing I have as a theory is that maybe one of the check valves between the pumps and the main/propel pressure relief valves is not working correctly, and that causes one side/pump to not build the correct pressure?
Help!
Carl Crawford
Well usually I can fix anything, but this machine has me stumped! So I'm here to beg the Hydraulic Gods to help me diagnose these wandering problems...
Intro: I'm new to heavy iron, we bought this machine to tear down an old house, do some stump and earth clearing, and dig a basement. 590D serial number incoming....
Machine seemed to work fine first 4-5 hours, then started to develop a problem where some functions would not work.. Lets call this failure mode 1.
Failure mode 1: Swing does not work at all (or very slow like an inch every 5 seconds), left propel does not work at all, boom 1/2 speed, arm 1/2 speed, bucket and right propel 100%. When this is happening, I can tease the left propel into working if I press the right propel, left propel, and slightly pull back on the boom handle. (Deere style control pattern) I think when this is happening that I can "hear" fluid or engine sound change slightly when the functions are being activated but not moving, like the fluid is being dumped off somewhere.
Fail 1 is the usual failure I will experience.
Sometimes it will flip to
Failure mode 2: Boom will barely lift itself, only enough to take the slop out of the pins. Right propel dead, arm 1/2 speed, bucket super slow. Swing seems to work, left propel will work.
So I did my own looking around and learned that these functions (failure mode 1) are all related to the rear pump section, and the left control valve side. We called Deere out to have a look. They sat in the truck awhile and read the computer manual about our "super old" machine, ran the machine a bit, and proclaimed that it "needed a new pump" for sure. (in hindsight, I should have been there to question their diagnostic methodology given that they never attached any gauges or flow meter to the machine)
Machine sat like this for awhile as it was super cold and frozen. I removed the pump, sent it off to be rebuilt. I drained all fluid that I could access, including vacuuming out the hydraulic tank, (was very clean) replacing suction filter, screen, pilot filter. Installed new pump, filled oil, primed pump and fired it up. Checked pilot oil pressure with gauge, around 700.
Machine was no change in operation. Seems to run fine for a little while, then all of a sudden the functions go out. When it goes out it is all of a sudden, aggressive stop. Usually will not come back, sometimes if I idle low for awhile it will come back.
So I dug hard into the workshop and diagnostic manuals. I started to suspect the regulator that controls the rear pump stroke control, maybe it is not working correctly and "stroking down" the rear pump to minimum displacement, and that is causing all functions on that pump to stop? When the left propel, right propel are pushed together and you add some boom control it shifts the combination valve and sends some front pump oil to the left propel and it works? I put my gauge on the rear pump regulator line and it seems to show pressure at the 300psi or so when no functions activated, and goes down to 40 psi or so when you are activating functions, but the function is not working. This does not change whether the function is working or not.
I don't suspect that the pilot or spools are not working, because when I stroke one of the "lame" functions, I can look over my shoulder and see the swing brake release line flex. The spools are moving and releasing the swing brake, even if the function is not moving.
So then I wanted to look at the spools, and combination valve. I cleaned the top of the control valve, and removed both spool covers. Combination valve moves nicely, same with the bypass valve next to it. All spools can be pulled up to the top of their bore, then dropped and they will slide right in nicely....
Except for the left propel spool! It was not super loose, in fact I had to twist and pull pretty hard to get it out. It did not want to come out or move nicely in the bore. So it seemed like a smoking gun, but it did not fit the problem that I was having. If it was siezed in the bore and did not move, that function alone would stop working but not affect all the others correct? If it stuck in an "open" position, the track would be stuck turning etc? The spool looked fine, no mars or marks. I micro-polished it anyway with some Crocus cloth. Still would not slide in nicely. Now don't judge me, but I ran an appropriately sized 1000 grit dingleberry hone in the spool bore and cleaned it up so that it would slide in pretty nicely. It hits a tough spot midway through, but once it is all the way seated it will move easily through it's small range of motion. Absolutely no change in operation, failure mode 1.
So I noticed the the arm (stick) would move the wrong way if I was trying to slowly move the arm out, so I started to suspect the circuit relief valve. You can tell that many of these have been replaced, as they are a brown color instead of yellow. I removed the two arm circuit relief valves and swapped them. Now it seemed to switch to failure mode 2! Coincidence? I have studied the hydraulic diagrams, and I cannot make myself see how a bad circuit relief valve could cause my failure mode 1 or 2. If you had a bad circuit relief, that function would be slow/lame in that direction but not kill everything else on the control bank side correct?
So I went to swap them back again and when I pulled one out I noticed the Oring and backup washer were half gone! (this could have been my fault when I swapped it really fast while being showered in oil from above, with my arm blindly shoved up the hole while sitting on a pile of 100 year old house rubble) So I got 2 sets of the rings from Deere this morning (all they had in stock) and put new rings on both of those circuit relief valves. No change, Failure mode 1 after it worked correctly for about 20 minutes. Shut down for awhile, fired back up and worked for a few minutes, then failure mode 2! I did play around with the arm stick while it was working, and it does seems like it will go the wrong way in both directions, it's just harder to see it in the "out" direction because gravity helps. I had to pull the arm all the way back in to see it happening. So this may be caused by a worn cylinder piston seal instead, put that on my list.
So I am getting low on ideas, I just can't think of anything that would cause these failure modes, especially when they change back and forth like that.
I am planning to order more orings and re-seal all the other 6 circuit relief valves.
I plan to disconnect the "aux" function hoses that are currently screwed together and confirm that there is not a huge leak across that circuit. (had a thumb on it previously we think)
I plan to plumb gauges into both pumps to see what the pressure is both when the machine is working, and when it goes into failure. (I probably should have done this first) One thing I have as a theory is that maybe one of the check valves between the pumps and the main/propel pressure relief valves is not working correctly, and that causes one side/pump to not build the correct pressure?
Help!
Carl Crawford
