POWER STEERING WON'T TURN LEFT UNDER LOAD REPLACEMENT PARTS NOT AVAILABLE

[Thumbs Up Farm]

I have a Massey Ferguson 40 tractor that is having issues with the power steering. I was using the tractor to feed hay with the FEL and loss steering ability :thumbdown:. The tractor will not turn to the left while the FEL is loaded. I can still use the tractor as long as I don't have a heavy load on the FEL. I can lift the front wheels off the ground with the FEL and turn either way just fine.

This is a two cylinder full hydrostatic steering system. My best diagnosis at this point is that the RH steering cylinder is bypassing and causing the loss of power when turning left. The RH cylinder applies the most pressure because it is on the extension stroke for a left turn. Of course, either cylinder could be bypassing and so I need to repair/replace both. There is also the possibility that the steering valve is at fault but most information says that is rare, and not likely.

So, here is my problem. I have to either replace the two steering cylinders or re-build them. Most information I have found points towards a rebuilt cylinder failing again because the internal tube that forms the bore of the cylinder is subject to wear and bulging/swelling in the middle which creates a bypass especially when the piston is at the middle of it's stroke. This, and the fact that the seal kits are not available from Tisco, and cost $75.00 per side from the dealer, have lead me to the decision to replace the cylinders.

The cylinders for this tractor are no longer available So, I plan to replace them with these 1.5X6X1 DA HYD CYL PINHOLE Obviously, some machine work will be required for mounting the tie rod ends, but aside from that, these have close to the same bore, stroke, and rod diameters as the old ones.

My question concerns the difference in the way the ports, bore/sleeves, are configured. The original cylinders have both ports on the same end of the cylinder casing and the new ones have one port at each end of the casing. The plumbing will work, as far as clearance hose attachment is concerned, but is there something else I am missing that will affect the function???

Anyone on here ever done this before? Any response or feedback is appreciated.

Thanks!

 

[Dave M7040]

Why not swap the cylinder from side to side to see if the problem changes sides?
Dave M7040

 

[clayhardock]

A cylinder that is bypassing will heat up. Hold the wheel to the left for awhile and then check the cylinders to see if one is hotter than the other. The hotter one is bypassing.

I would take the cylinders to a local hydraulic shop and get a quote for rebuild or replace. Tell them your concerns about the swelling. They can rebuild you cylinder using the same rod/piston and just give it a new new tube in the same configuration. Probably for cheaper than a whole new unit that you'll then have to mess around with. The rod is the expensive portion of the cylinder.

 

[Billrog]

Is it a tandem hydraulic pump system if so one is for the power steering and you may want to check that it's putting out pressure before rebuilding the cylinders.

 

[Thumbs Up Farm]

Thanks for the input. There are several ways to test the cylinder(s) to determine which side if not both is bypassing. However, the Massey mechanic recommending I repair/replace both at the same time because if one is already failing, the other can't be far behind, and I agree with him.

I have already decided to replace both cylinders using the units in the link above. There were several reasons for this decision.

1.) Both cylinders are worn and appear to have been rebuilt by the previous owner.
2.)Big Deans CD says these cylinders are prone to swelling and repeat seal leakage. So, another repair is likely to fail again and I believe the sleeved design is not as robust as the single barrel design.
3.)New seal kit is only available from AGCO at a cost of $75 each side. New cylinders are $89 each. So added cost is on around $30 for both cylinders.
4.)The tie rods on one side are completely shot and the others are loose, so I plan to replace them all to eliminate the slack in my steering that has been problematic ever since I bought the tractor.
5.)I have complete machining/fabricating ability for necessary modifications. So, cost for this work is $0. I should be able to complete mods for both cylinders in 1hr. or less.
6.)Securing all the parts and making modifications in the shop allows me to change them out in the field with limited down time.

So far, with another members PM, the only issues may be a slight difference in bore diameter. I can only measure the outer diameter and my best guess is that the original design is 1 1/2 inch bore. A slight difference could mean slower or faster steering response, but I don't think the difference will be noticeable since It can't be off by much (1/4'or less). Are there any other issues I may have missed?

 

[Leejohn]

Do you know why it has a internal tube for the piston? You might find out if you use the cyls that you posted a link to well not let the steering wheel to come back to the same spot all the time. Have you seen a parts list of the cyl, if you have did it show any valves made into the piston?

 

[Thumbs Up Farm]

Do you know why it has a internal tube for the piston? You might find out if you use the cyls that you posted a link to well not let the steering wheel to come back to the same spot all the time. Have you seen a parts list of the cyl, if you have did it show any valves made into the piston?

I am not sure why it has an internal tube for the piston other than providing for both hoses to be attached to the fixed end of the barrel instead of one hose at each end. I have attached the parts list picture of the cylinder. I don't see any valve, so maybe not an issue??

 

[Leejohn]

The inner tube gives each cyl the same amount oil as the other no matter where the cyls are at. The tank in the pump is real small and it keeps from running out of oil in it. So after all the air is out of the system the steering should return to the same spot.I have forgot what that steering system is called, but as you turn the wheel you are pumping oil to a cyl. So you can see why a little air can make the steering ack funny. Your steering head tank might not be big enough for the cyls you linked to. Do you think a single piston 2 rods cyl would mount up some how?

 

[Thumbs Up Farm]

It is called a full hydrostatic system. There is no linkage that ties to the steering wheel at all, only hydraulic hoses. I have never really paid attention to the steering wheel, but I don't think it will spin itself back to the center position like a linkage driven steering wheel does when you release the wheel. I am pretty sure the wheels stay turned in the direction I last turned them until I rotate the steering wheel the other way, back to center.

The two cylinders should get the same amount of oil/pressure because they are connected with a "T" on the same two hoses. One hose feeds the extending end of the RH cylinder and the retracting end of the LH cylinder simultaneously. When the cylinders are "steered" the other way the oil goes back to the pump and is then pumped to the opposite ends of the same 2 cylinders, using the same oil. I will have to work the air out when I install but, once the air is out of the system, and the pump reservoir is full, there shouldn't be any issue??

 

[Leejohn]

I didn't mean it would come back to center by itself. When it's turned to center the wheel is in the same spot as it was before you turned it.
The shaft takes up room in the cyl and the oil on the outside of tube makes up for your shaft.