Had to pull the rotary manifold out of my JD490 / Fabtek harvester the other day. Marked the top lines as they came off, the bottom steel lines are pretty obvious. Got it all back together yesterday and now I have a couple odd issues that were fine before. The bucket cylinder will not retract, it will extend, but not retract. The stick works fine, the boom will go up and down, but I don't think it's forcing down pressure - it stops when it hits the ground and will not lift the machine off the ground like it did before. I reved the machine up a bit over idle, but did not bring it up to full throttle as I can hear a different noise coming from the hydraulic pump area, it goes away when shutting off the hydraulic activation lever - sort of like the pump is meeting hydraulic resistance. I removed the retract hose from the bucket cylinder and stuck it in a bucket, was going to check for flow when activating the joystick, but I have oil flowing out of it as soon as the hydraulic activation lever is put on, so it has oil there all the time, which must be wrong. I also noticed the head hoses "jump" when turning on the activation lever which I don't ever remember them doing before. I double checked my lines going to the manifold and they are correct. I pulled the return hydraulic filter. It was not dirty, but there was oil pressure in there, when getting the bolts loose a fair amount of oil did run up and out around the seal, even after venting the fill side of the tank. Is this normal? I am really lost here as these functions were fine the other day. I had to remove the manifold as it was leaking into the swing bearing area. What on earth did I do wrong?
I would say you introduced a fair amount of air into the system and it is air locked. Try cracking the line at the cylinder and see if you get any bubbles.
Hopefully you didn't leave a rag or something in the lines some where if you used them to cover open system.Also might be air in system.
Thanks, I used zip lock back and gorilla tape over all the ports, so no rags in there for sure. No air in the pump as I checked the purge port there, will try a line.
You have debris from the rotary valve's failed seals in the bucket spool. Pull the spool out, remove any offending material, reinstall and try it.
Good day Sir The symptoms you describe are ver similar to that of a piston breaking away from the piston rod, are their any clunking noise from the cylinder? Kind regards Uffex
Is this a 490D or 490E?
Joe - its a 490D, Uffex, I don't believe it is a broken / separated piston, as I also don't have down pressure on the the boom - ie -it won't lift lift the machine off the ground, seems to be more of a gravity down, but it will lift up. The book says its an open center system, but in trying to figure out what is going on I discovered that I have hyd fluid - low pressure at idle, flowing into each line running into the bucket piston on both sides at the same time, even without activating the joystick - is this normal? Thanks for all the help. If it makes any difference I did pressure wash the engine bay, pump, and valve area to get the built up crap that was in there (machine new to me). Could I have knocked something loose at that time?
If there is pressure on an open center system you most likely have a problem with the valve body. If it were a closed center system with standby pressure you are looking at higher clearance between the spool to the bore but with an open center there should be no to little standby pressure. What happens when you disconnect the pilot lines? How are you tapping into the system to measure the pressure? What is the pressure to the cylinder?
Hi Mike, I have not disconnected the pilot lines yet, should I try at the valve body? I don't have a pressure gauge - can get one here tomorrow, so I don't know the pressure to the cylinder, when I opened the cylinder line and ran it into a bucket it was like a garden hose not on full blast if that makes sense, the engine was at idle. Thanks
Sounds like heymccall's advise should be followed and remove the spool