drifting backhoe

[tabacman]

So i replaced a hose on the woods bx70 backhoe that was leaking badly only to still have a problem with boom swing drift.
When swinging the boom left or right and releasing the control back to center the boom starts to drift back to center with no input. This is initially how i determined the fact of a blown hose. Now with new hose in place i still get the drift issue with no leaks -so far. I will do another leak check later to be sure.
Any ideas what would cause this?
I have gone over the swing cylinders and can find no leaks there - before and after the boom lift hose issue.
The backhoe will be usable enough - but i dont want to be doing further damage to more expensive parts.
Thanks.

 

[AKKAMAAN]

Any ideas what would cause this?

Most likely a failing piston seal in one of the swing cylinders....

 

[J_J]

So i replaced a hose on the woods bx70 backhoe that was leaking badly only to still have a problem with boom swing drift.
When swinging the boom left or right and releasing the control back to center the boom starts to drift back to center with no input. This is initially how i determined the fact of a blown hose. Now with new hose in place i still get the drift issue with no leaks -so far. I will do another leak check later to be sure.
Any ideas what would cause this?
I have gone over the swing cylinders and can find no leaks there - before and after the boom lift hose issue.
The backhoe will be usable enough - but i dont want to be doing further damage to more expensive parts.
Thanks.

You may not have any external leaks

You say you check all around for leaks, but did you check for cyl internal leaks?

Like Akkamaan said, maybe piston seals leaking, or perhaps the spool is not centering when you release the lever.

 

[tabacman]

Thanks guys. I suppose i should check all the cylinders i have been working it pretty hard getting out some stumps. Whats best/cheapest way to test them. Are you guys of the opion that a cylinder repair is worth doing yourself or taking to a pro.
The controls mechanically look and act like they always have - so barring internal damage i think its in good shape. **** thing only has 50 hours on it. Is it a telling sign if both left and right are drifting? seems like 1 would go vs both at once - but what do i know. Again thanks for any advice or experiences you all care to share.

 

[dfkrug]

Is it a telling sign if both left and right are drifting?

The problem is with your valves or the linkage to it. I have seen newish
hoes where the joysticks don't move smoothly, and I find out that the
little heim joint linkages have never been oiled. A failed piston seal still
needs a path for oil to go and you said there were no leaks. So that
leaves the valve.

 

[Piston]

Sorry I can't help with your problem, I only clicked on this thread because the title led me to believe that you literally were drifting your backhoe! Man that would be cool to see!

 

[tabacman]

Sorry I can't help with your problem, I only clicked on this thread because the title led me to believe that you literally were drifting your backhoe! Man that would be cool to see!

Thats a visual i didn't have when i titled the thread... but I suppose I'd rather be doing that than having to tear open the control valve body.

Thanks to all for the advice. I will look over the control linkage again and single out the swing spool and see if that can be inspected without undue pain and suffering. I agree that the fluid has to go somewhere - and the spool leaking would explain both sides being out of whack.

Thanks again.

 

[twoone]

Just wondering did you bleed the system after the repair? Am Thinking there still it might be air in the cyl.

 

[J_J]

I don't know of a BH that will spring to center, so something is making it move. The valve might be spring center, but the boom should stay where you left it.

If the spring to center spring is not tight, it will probably cause the cyl to go one way and stop, but not at the center of swing.

A good valve will lock the cyl in place, and if it moves, then it is probably the piston seals leaking caused by weight, pushing or pulling on the cyl rod.

If you think it is air, then the air should be expelled by cycling the cyl. The only other thing is that fluid is leaking from the valve to the swing cyl and causing it to swing, but to stop at the center of swing is a mystery.

A non centered valve would send fluid to the cyl, but it would make the cyl either push or pull to the stops.

If the swing cyl is a double rod , same size, and the valve was leaking through both work ports, maybe try to center.

Remove both hoses from the BH swing valve and start tractor and see if any fluid is leaking out the swing cyl work ports.

 

[twoone]

since so many other cures have been tried I noted that nobody suggested to bleed the system it seemed like a good idea to me at the time that's why I suggested it. My next thought is have you contacted the mfg. and talked to there customer service some times the problem has come up before and they may have an answer for you. just a thought. Paul