Go Bottom3Pt Hitch Problem
 | Bvan
Join Date: Jul 2003 Posts: 16 New jersey 
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2002-07-06 40100
I am rebuilding a 1988 John Deere 850. I just replaced the loader control valves. I now cannot get the hitch to raise and there seems to be a sceeching noise coming fron the valve large valve below the seat. It was working prior to the repair. Could someone please advise me on this problem.
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| TomG
Join Date: Feb 2002 Posts: 5406 Upper Ottawa Valley 
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2002-07-07 40111
That sounds like a relief valve opening. A tractor shouldn’t be run long when the relief is opening. Oil overheats and pumps are damaged.
Sometimes you hear of such a problem when an owner orders and installs a 3rd party valve. Some valves may be used on either open or closed centre systems. They come with a plug installed for closed centre use. The plug has to be removed for open centre systems.
There are other possibilities for obstructions depending on the valve type and plumbing. ....
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| Bvan
Join Date: Jul 2003 Posts: 16 New jersey
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2002-07-07 40123
Thanks for responding. I have a JD replacement valve on the tractor. I am certain that I have it set up the same way as the old one. One of the valve shafts was worn in the old one and the c ring grouve was gone causing the valve to fail. The loader is working fine so I figure the pump is good. When you start the the machine up the RPM's jump around a little and start to drop off a little but when you raise the bucket to move the tractor they come back up. I haven't run it long enough to see if the RPM's drop of again. The 3 point remains in down position with no pressure, it can be lifted by hand. If it is a relief valve which one should I look for? I should mention that the previous owner had a backhoe on the unit but the 3 pt seemed to be working fine before. maybe their is an adjustement I am missing. Thanks again I am greatfull for the help. ....
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| TomG
Join Date: Feb 2002 Posts: 5406 Upper Ottawa Valley
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2002-07-08 40140
I have to talk as if the 850 is just like my Ford 1710. They are about the same age I guess.
The first thing I'd do is change my diverter valve from auxiliary to remote. The remote position takes the entire auxiliary system off-line and powers only the 3ph. It's an easy way to check if the problem might be something like a stuck unload valve in the 3ph.
From the description, I'd expect the 3ph to work normally with the diverter in remote. The screeching sounds like the system relief valve opening due to an obstruction in the loader valve or PB line. If loader worked, the 3ph didn't lift and there was no screeching I might think of checking if the PB and tank return lines from a power-beyond type loader valve were reversed.
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| Bvan
Join Date: Jul 2003 Posts: 16 New jersey
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2002-07-08 40166
Tried to changing my diverter valve from auxiliary to remote, no change. The valve did not shut off. To be more specific the noise coming from that manifold does sound like a backing up valve noise, heavy fluid sound. Thanks again for help. ....
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| TomG
Join Date: Feb 2002 Posts: 5406 Upper Ottawa Valley
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2002-07-10 40227
There is a difference between the sound oil under pressure makes going through valve orifices and an open relief valve. I describe a relief valve sound as a screaming. Some people say it sounds like a car's power steering turned to a lock.
With the diverter valve in 'remote' the loader valve should be in the system in a typical hookup, and the system relief valve sees both the remote and auxiliary systems. Again in a typical hookup, PB return oil from a loader valve goes back to the manifold block and on through the same high-pressure tube used by the remote system.
If the loader works in aux (it shouldn't work in remote) and the 3ph doesn't lift in either position, then the loader valve and plumbing as well as the system relief valve are not likely problems. On the other hand, it is a little hard to ignore the coincidence that the 3ph worked before the loader valve was worked on and then didn't work. Thinking of coincidence, I don't suppose there's any chance that the 3ph quadrant lever linkage could have become disconnected from the control valve arm while working on the loader valve?
I'm not sure where the system relief valve on an 850 is. However, most 3ph's have their own relief valves that generally would be under the seat. These relief valves can fail, although I believe that usually very weak lifting remains. Hope all this at least helps you to think through the problem.
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| Bvan
Join Date: Jul 2003 Posts: 16 New jersey
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2002-07-10 40257
Tom I have got plenty of lifting pressure. So let me run this idea by you just in case I am missing something. I just bought this piece. When I test ran it the 3pt worked. It worked when I got it home. It only had a non filled weight box on the back about 50 pounds. I did raise it will standing on it. Now I more familiar with full size tractors than compacts. Could there have been a un-noticed noise coming from a diverter valve about to go bad? possibly. I was playing around moving little dirt out back before the loader valve broke. As I mentioned before the it was an internal faliure ( curl lever side). When it broke it also blew a highly worn hydro line on the bucket ram. If it is the diverter I know that I can't fix it all myself but considering that I am handy is it possible that I could remove the manifold and just send the valve to the dealer rather than the whole tractor. I really appreicate your time. Thanks again ....
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| TomG
Join Date: Feb 2002 Posts: 5406 Upper Ottawa Valley
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2002-07-11 40266
I hope I'm not starting a wild goose chase by assuming that a relief valve is opening if that isn't the sound described. It's the sound made when a loader cylinder is at the limit of its travel and the control valve is held open, or when the 3ph is working at a load it can't lift. Usually the engine is under heavy throttle as well. If the farm tractors you’ve work with had closed centre hydraulics, these descriptions may not sound familiar.
If it's a relief valve sound, I wonder if I've got the situation right? In remote the 3ph lifts and there is no screeching. In aux, the loader works but the 3ph doesn't and there is screeching. If that's the situation, a further check is if the screeching goes away when the loader is working.
If that's what you're dealing with and the screech goes away when the loader is working, then the problem likely is an obstructed PB line. My assumption here is the loader valve assembly is a power-beyond type that has two return lines from the outlet section. If the screeching is present all the time, then it's likely an obstruction in the valve assembly or aux system high-pressure line.
System relief valves usually are in the block ahead of the diverter valve, so the relief valve sees both systems. An obstruction anyplace in either system can open the valve, so the location of the sound doesn't necessarily locate the problem. If there's plenty of lifting power, then the relief valve likely is doing its job.
I don't think of a diverter valve as something that fails. There are o-rings that might allow external leakage of seepage between the remote and aux systems. However, it certainly is possible to get junk lodged in the diverter. Junk from a ruptured hose could have gotten into the lines, during installation of the new valve or simply from dirt in female quick-connectors during implement swaps. I think I’d do a litle more checking before tearing into the system, but rebuilding a manifold block shouldn’t be too difficult provided manuals are available. ....
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