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John Deere 75 Loader problems

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S B
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2002-03-26          36753


Can anyone tell me what could be wrong here? I bought a 75 loader for my 850. I bolted it up and connected the quick connect lines. I was able to raise the bucket a few feet but not roll it. After raising and lowering a few hundred times, it went up 1/2" higher each time, until full height.
I noticed that the control lever on the side of the seat, does not have the movement that the raising lever has. The lever almost feels like it's stuck and just clicks a little.
I assumed the worst and priced a new control valve from JD.
They want 700.00, of which I can't afford.I tried swapping the lines in different configurations, but I can only lift it hooked up this one way, still with no roll. I don't think I have down pressure either. I used it to pull a heavy diesel out of my dozer, so it lifts. any info or ideas would help Thanks Steve




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John Deere 75 Loader problems

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greenjeans
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2002-03-27          36773


Steve,

First, let's back up and go back to the instalation. have you checked hydralic fluid level? If the loader cylinder and lines were drained of fluid, then you may need to add more.

Second,If you have the loader plumbed correctly, I would say it is a valveing problem.

Hydralic valves are not that hard to rebuild. And if they have not been used much, spools do tend to seize. Also, O-rings and springs can break and lodge themselves between moving parts within the valve, and plug small ports in the orafice of the popit valves.

Old hydraulic hoses have been known to blister internaly and seperate. This can cause all kinds of funny stuff to happen. Oil will flow one direction through the line, but not the other. Or maybe flow flow poorly one direction, and block the line when the oil changes direction. Small pieces of rubber from the hose can lodge within the valves of the system.

Quick couplers can also fail and I would suggest trying new male ends to eliminate this problem from the equasion.

I think you have more than one problem.

On the control lever on the side of the seat, my educated guess whould be sezure from lack of use.

The valve that you are useing to lift probably has a plugged port or stuck popit valve.

Again, as always, these reports are subject to change without notice. Past history does not garauntee future success, and some people can and do loose money.

Keep me informed, and I will try to help as much as I can. ....


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steve arnold
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2002-03-27          36782


check fluid and all those others that Mr. Greenjeans mentioned and this might be SITD but my 970 w/80 loader has movement lock that locks all joystick movement or just bucket curl. ....


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Sb
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2002-03-27          36792


Is it a big deal to rebuild these control valves? I checked fluid level in the trans case. I think the hydro shares the same fluid. The level was right on. I'm going to replace the hose ends ASAP. where would I get rebuild seals for this besides JD? Do they carry them? I am pretty mechanicaly
inclined, but I do not know anything about these animals.
Thanks Steve ....


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TomG
Join Date: Feb 2002
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2002-03-28          36801


Steve: I'm guessing that the loader was bought used and installed by yourself. I have no way of knowing if the joystick (again I'm guessing) linkage movement is normal. I do think it's be unusual for both valves to seize at the same time, so maybe eliminating some simple possibilities before tearing into the valve would be good.

First, as Steve A mentioned, there's the possibility that the linkage itself isn't moving. The lift control probably has a float detent, so if the valve goes into a detent and stays there, then the movement probably is normal and the valve isn't seized.

To check the plumbing, I'd listen to check if the relief valve is opening, which would indicate an obstructed high-pressure line. The 3ph should definitely be in neutral mode while checking the loader operation. I'd also check to see if the 3ph works. If it works, then check to see f the lift is stopped by operation of a loader valve. In many hook ups, the 3ph should stop while auxiliary system hydraulics are operated. Basically, if the 3ph works and the relief valve isn't opening, then the loader valve has an open centre and there's a good return to the sump. If it's a new valve and the relief is open all the time, I'd suspect that a plug used for closed centre system operation wasn't removed.

I'd check for certain that the quick connectors actually are seated. A closed line on either side of a cylinder can cause pretty much you describe. However, in such a case, there's a little movement and then the relief valve will open.

I'd identify the loader valve is a power beyond type, which it probably is. PB valves have one line to the inlet section and two return lines from the outlet section. One return probably goes back to a port on a hydraulic manifold block. This is the PB return, and it's likely plumbed OK if the relief valve isn't opening. The other return line should go directly to the sump. this is the low-pressure or tank return line. It handles exhaust oil from the passive side of driven double acting cylinders. Double acting cylinders have oil on both sides of the piston, when pressure on one side of a cylinder moves the piston, oil on the other side has to have some where to go. An obstructed tank line would produce something like what is described.

In terms of rebuilding a valve assembly, I haven't done it myself. I wouldn't hesitate to tackle one, but I'd want a good exploded parts diagram. There are a bunch of parts in a valve assembly.
....


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sb
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2002-03-28          36805


My 3point hitch is opperating fine, up and down. I have 3 levers total. One lever by itself operates the 3ph. The other 2 levers control the loader. One of the loader levers lacks movement. I think this is causing the bucket roll funtion not to operate. The other loader lever moves freely, alowwing me to lift the loader. I am going to change the quick connects. Then I will remove the valve.
I'm not sure how long this loader sat. It appears to be in really nice shape. Thanks Steve ....


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sb
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2002-03-28          36806


One other questi, would'nt the loader operate reguardless as to how the quick connects are plugged in? I now the levers would not feel right,"positioning" but they still should operate the cylinders right? thanks Steve ....


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TomG
Join Date: Feb 2002
Posts: 5406 Upper Ottawa Valley
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2002-03-28          36810


A quick shot at an answer because my dog really wants out his run to better harass a squirrel.

A quick disconnect on either side of a cylinder will pretty much lock the cylinder in place, but the valve will seem to operate normally--the relief valve will open though. If the connect is on the pressure side of the cylinder, then operation of the valve closes the centre, which blocks the high-pressure line.

Operation of the valve also opens ports to the cylinder--one for pressure and one for return oil. The pressure side connect isn't seated, there's no place for the oil to go and the relief valve opens. If the connect on the passive side of the cylinder isn't seated, pressure is developed on one side of the piston, but there's no place for the exhaust oil on the other side of the piston to go. The cylinder sort of jumps a bit and then the relief valve opens. Usually quick connectors are either seated or not seated. I guess a gimpy one could sort of inch a cylinder along.
....


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TomG
Join Date: Feb 2002
Posts: 5406 Upper Ottawa Valley
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2002-03-28          36812


Back from dog, breakfast etc. Had a quick thought that just might be the problem. First, the dog problem: A squirrel was hanging from the bottom of a bird seed bag looking like a furry red woodpecker and swinging the bag around. Squirrel finally got the bag hung over some small limbs and was sitting on top of it munching away. Dog decided that a calmly munching squirrel was acceptable as opposed to squirrel doing a trapeze act. Everything resolved except for a few grumpy birds who probably blame me.

The hydraulics: I guess by three levers, you mean two on the loader valve and a separate quadrant lever for the 3ph. My loader valve has three control valves, one of which is for a rear circuit. Quick connectors can be tricky is you haven't connected them often. They can seem seated when they aren't. Seated ones can be pulled off with a good tug, but there is a definite feel that something was connected if it was seated. It's possible for the male ends to just sit in the sockets without being actually seated--done it myself a few times.

A common learner's problem is that if lines are disconnected without setting every thing on the ground, then one line from the loader will contain pressure, which makes depressing the ball so the connector can seat difficult. The same thing can happen if an implement is removed on a cool day and remounted on a hot day. It's not uncommon that lines just can't be seated. Usually manually depressing the ball on a male end cures the problem and can be done by pressing the rag wrapped fitting against a tire. A rag is desirable because a good squirt of oil results. Sometimes a ball needs to be whacked with a soft-faced hammer. I've had to loosen fittings to bleed off pressure from particularly stubborn ones--I never can find a soft-faced hammer anyway. Sure would be good if something like this solved the problem.
....


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GREENJEANS
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2002-03-28          36814


TomG is raising some very good points. Those quick couplers can reall be a pickle and cause all kinds of diagnostic nightmares. They can be a big oily mess too. Just make sure the loader and bucket are on the ground or supported before you attempt to remove any pressure from the plumbing.

Please be carefull!!!!!!!
....


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