Moline 708 steering cylinder will not move either direction

[Mark Alloy]

I have 1700PSI + at remotes.With guage plumbed in series in steering cylinder supply line I have no pressure and with guage plumbed directly to steering supply port on hyd. pump I have 650 PSI +. Does this sound like with guage plumbed in series in steering supply oil is passing straight back to oil tank.
also,Is there a trick to unscrewing head out of cylinder? any help would be greatly appreciated.

 

[flying belgian]

I have 1700PSI + at remotes.With guage plumbed in series in steering cylinder supply line I have no pressure and with guage plumbed directly to steering supply port on hyd. pump I have 650 PSI +. Does this sound like with guage plumbed in series in steering supply oil is passing straight back to oil tank.
also,Is there a trick to unscrewing head out of cylinder? any help would be greatly appreciated.

I wonder if the piston came off.

 

[Tony in SD]

There is a rubber boot on the top of the cylinder with a valve connected to the steering arm. If that boot is missing or torn, there is a fair amount of dirt in the valve and it can not move far enough in either direction to activate the cylinder. You will have to clean the valve and replace the rubber boot.

 

[moresmoke]

The pressure gauge in the supply lime will not show pressure unless you are trying to steer. It is an open center valve and will pass to return when centered.

The edge of the cylinder barrel is crimped into a slot in the end plug. You need to drive that out, then unscrew. Can be difficult to get apart. As Tony said, possibly packed with dirt. A new boot can be fashioned out of a CV boot if needed.

 

[Mark Alloy]

The pressure gauge in the supply lime will not show pressure unless you are trying to steer. It is an open center valve and will pass to return when centered.

The edge of the cylinder barrel is crimped into a slot in the end plug. You need to drive that out, then unscrew. Can be difficult to get apart. As Tony said, possibly packed with dirt. A new boot can be fashioned out of a CV boot if needed.

 

[Mark Alloy]

Thank you for your help Moresmoke but I'm not through.Do you have time for a little more help with this 708 steering cylinder?

 

[used red MN]

Thank you for your help Moresmoke but I'm not through.Do you have time for a little more help with this 708 steering cylinder?

He is a regular here, just type out what you need either him or someone who knows will attempt to answer. That’s how a forum works.

 

[Mark Alloy]

Moline 708 steering cylinder dosen't move in either direction.Hydraulic pressure is close to specs.at remotes and steering supply line.
With cylinder disconnected from left front wheel,I can get no movement from steering cylinder at all.Is my steering pressure bypassing somewhere inside cylinder and returning to hydraulic tank.

 

[Tony in SD]

If I remember correctly you need to have some resistance on the cylinder in order for the valve on the cylinder to engage. So disconnecting the tie rod would be counter productive. Did you check for movement of the valve? If it moves, does it move far enough? Remember if the rubber boot is missing, there is dirt in the valve body restricting its movement. That dirt needs to be cleaned out and kept out. I am reasonably sure that if it is not your only problem, it usually is part of your problem. We owned and used a MM G708 for many years. If dirt gets into the steering valve body on the cylinder, it will take a strong man to turn that monster.

 

[Mark Alloy]

I have threaded cast iron plug removed and everything in that end of cylinder is clean.The Flexure and ball stud shell are still in place.The valve is still in place and there is a spring holding it pulled up tite against valve spool.Is there a way to pull valve spool out in order to clean it.

 

[Mark Alloy]

Are there any parts available for 708 steering cylinder.New or used?

 

[Tony in SD]

I have threaded cast iron plug removed and everything in that end of cylinder is clean.The Flexure and ball stud shell are still in place.The valve is still in place and there is a spring holding it pulled up tite against valve spool.Is there a way to pull valve spool out in order to clean it.

Been over 40 years since Ive fixed one. Sorry but I dont remember and Im not sure I can find the service manuals anymore.
Might try Welters Farm Suppy for parts, 417 498 6496 Verona MO

 

[moresmoke]

Once the cast plug is out, the ball stud should be able to be removed and the whole valve assembly should come out of the cylinder. There are 4 little o-rings that seal the valve to the cylinder barrel. Its just a simple spool valve that is operated by the ball stud. I resealed mine last summer, it is a bugger to get back together and not cut the seals. Its possible your piston seal could be bad, or the piston is loose, but it is a welded cylinder and would have to be cut open to service.

I have never needed parts beyond seals, and those I just sourced by dimension. Welter’s would be my first call if looking for parts.

There are at least 2 different styles of cylinder, but I believe they are interchangeable on the G-VI through G708. If you want to look for a used one.

 

[Mark Alloy]

I have the threaded cast plug out and the ball stud and ball bearings .The next part which is solid has a what appears as the head of a valve and is held in by a spring on back side which cannot be seen.Does this section come out of cylinder or is it the section that is welded to the tubular part of cylinder?
I appreciate your help with this .I operated this old tractor for many years after my dad outgrew it back in the late 70 's.I pulled it out of a shed around 4 years ago to restore it.It was not a great candidate for restoration but it was a classy old tractor in it's day so I was determined to bring it back to life.This steering cylinder has stopped my progress dead in the water,so please bare with me.LOL! if I don't get this project finished my pall bearers will have to.

 

[moresmoke]

The whole valve assembly will slide out of the cylinder.

 

[Mark Alloy]

The whole valve assembly will slide out of the cylinder.

valve assembly is out.I have removed the inner snap ring from the opposite end. Should the rod come out now?

 

[moresmoke]

Once you remove the inner retainer it should all come apart. Pay attention to the order of all the parts.



Hopefully you can see the image well enough. Agco Parts books and mobile are not the best combination.

https://parts.agcocorp.com/us/en/ap...ed90-8c236bd1996d&name=POWER STEERING BOOSTER

 

[moresmoke]

Double post.

 

[Mark Alloy]

Double post.

I've got a good tech manual and parts book as well.Thanks for your help.I appreciate it. Mark A.