back hoe

[tnott]

I have a 2007 mahindra 3710 BH It has hydraulic pressure to move the boom to the right but not to the left. With no pressure applied the boom slowly fades to the left. This has a single cylinder to move the boom left and right rather than the conventional two cylinders.
I was told that the problem was most likely at the upper control valves. They feel as though they are moving the correct distance to open and close the valves.
This began after using the boom to smack a tree stump a number of times to help loosen it. I did not notice the problem until the next day.
Also the hydro transmission tends to creep? Doesn't seem to find the true neutral. I have laid under the tractor,looking for an adjustment. There are more levers/connections than I can easily follow. Any one know the proper way to adjust these? I do not have a dealer near, so am looking to do these myself.
Tom Nott

 

[manganos]

I had the same issue on a Mahindra hoe. I ended up taking the hoe controls apart and put them back together. One of the controls got "stuck" forward and had to be put back to the factory location. Easy enough but you will need basic hand tools.

 

[bindian]

My 511 operator's manual says never swing the bucket into anything. You have some trash in a control valve. Pounding something to loosen it works on tractor parts also. Quite possibly you have a nick in an o-ring or something broke loose with the banging and lodged into an o-ring. Not sure with a single swing cylinder how it is plumbed. With dual swing cylinders on my 511, it can be cylinder bypass. Mind creeps to the right, but I just engage the centering lock with not using the BH.
hugs, Brandi

 

[DiskDoctr]

As with Bindian, I'm not sure about a single cylinder system, but on my Case 580K with two opposing swing cylinders, I had this problem with one.

I had the local service guy come and repack the cylinder and that was it! He was there about 30 mins and did it while still on the machine.

Look for any leakage around the piston (wiper seal) of your swing cylinder.

If it is in the controls, there are others here who are better sources to help than I

- JC

 

[LAWALLSTRACTOR]

I would agree that, because the problem is only in one direction, the problem is in the control valve. I think if the problem was with the cylinder seal, considering the single cylinder design, it would be a problem in both directions. I always tell my customers with backhoes, that when something isn't moving, don't go banging on it, cause that is when you will break your equipment.

 

[DiskDoctr]

I would agree that, because the problem is only in one direction, the problem is in the control valve. I think if the problem was with the cylinder seal, considering the single cylinder design, it would be a problem in both directions.

You may be correct, but my thought was with the single cylinder, perhaps it will retract but not extend, or vice versa depending on the mounting. I thought maybe a seal in the cylinder was leaking.

I could also see it being a control issue where the spool is over or under traveling or an internal leak.

Hey tnott-
If you move one of the other levers while swinging left, will it then swing left?

- JC

 

[LAWALLSTRACTOR]

The cylinder has the seal on the center of the piston or rod what ever you want to call it. Depending on which side you push the oil in, it moves the piston one way or the other so I would think if the seal was leaking it would leak both ways. Just my thought.

 

[DiskDoctr]

The cylinder has the seal on the center of the piston or rod what ever you want to call it. Depending on which side you push the oil in, it moves the piston one way or the other so I would think if the seal was leaking it would leak both ways. Just my thought.

Yeah, that's one of the things that makes hydraulics tricky- cylinders tend to hide their problems

Our last cylinder (dipper on the hoe) had one of the seals on the piston with a nick in it. It would work okay as long as you didn't extend all the way. Retraction was fine, and about 1/2 extension was fine. When extending all the way, the fluid that had bypasses the seal and entered the space between the piston and the wiper seal, then after about 1/2 extension, the piston would force the fluid past the wiper seal in a thin, but gloriously high fountain of yellow (fluid with air from the leak).

Upon retraction, it would suck the fluid back in.

The seal wasn't completely gone, the cylinder was mounted vertically, and the gland and other seals were in pretty good shape. We put a new kit into the piston and gland and got an education in how stubborn red loctite on a 2 5/8" (IIRC) bolt can be.

You're probably right about the valve assembly- I don't usually work on those and it sounds perfectly reasonable. I was just offering a little experience to rule out the cylinder. A full extension and retraction without any leaks would be a good sign- even if it needed some help in one direction

In any case, maybe folks will enjoy the read- especially if they've seen their own "fountain" !

BTW- Trying the swing while holding another lever can uncover a valve or passage problem, too. Had that on an International years ago.

Hope to soon see what the problem and solution is. Good luck tnott!

- JC

 

[bindian]

I always tell my customers with backhoes, that when something isn't moving, don't go banging on it, cause that is when you will break your equipment.

Yep, you turn her around and ram her with the front end bucket. Just kidding.
hugs, Brandi