Backhoe Backhoe hydraulic problem

[Rowski]

I have got a problem with the hydraulics on my NH 759C (have used it about 10hrs). I have lost some power in the boom for moving the boom away (down). Moving it up it has the power it should. Everything else works great. When working with the hoe it seems like the boom is in a float position. I do have a float kit installed. Seems like something may be caught in the valve. Is there some way to try and flush the fluid out by moving the levers in a certain pattern or is disassemble required. Could it also be that the float valve is stuck in the float position. Another question would it do any harm to keep using it the way it is. Appreciate any advice.

Rowski

 

[Anonymous Poster]

Don't know what the problem is but was intrigued by a comment you made.

What is a "float kit" for a backhoe? Every backhoe I have used can be made to "float" for doing grading or raking branches by just operating the two levers at the same time.

I'd tell you which positions on which lever to use but I CAN'T THINK OF THEM! (I THINK it's boom up and dipper in) I could do it on a second if I was sitting on the tractor but for some reason can't visualize my hands doing it. Kind of like listing which muscles you use to walk, you can't talk about it, but you can do it!

That thing has really become an extension of my arms I guess!

del

 

[Rowski]

del, the float kit was put on by the maufacturer of the hoe. What it does (it only works for the boom circut) if you move the lever for the boom forward it lowers the boom if you move it even further it move into a detent position allowing the boom to float while you curl or crowd or swing the bucket. I have only used the hoe for a little bit. The float works well if you curl the bucket so the teeth are not digging and then crowd the bucket it leaves the ground pretty smooth and compacts it slightly (more consistantly anyways). Will be ordering a thumb this week. Than it will be like a BIG arm with a two fingers. /w3tcompact/icons/smile.gif

Rowski

 

[Anonymous Poster]

That seems like it is doing the same thing as lowering the boom while you pull the dipper in.

(I'm still trying to figure out which limb you'd use on one of those small excavators that also has a pivoting boom or dipper stick! Hey I've got it, there must be another long lever you operate with your mouth!)

 

[Anonymous Poster]

Wow, never knew you get a float position on the hoe boom. I can see where just a gravity pushing the bucket down would be nice for finsh work. Is this feature an option with the NH hoe or is it standard equipment?
On the boom, ok up but weak down, as you know, float vents both sides of the dipper ram to sump. It seems that when you go up you are managing to close at least one side of, the double sided float vent to sump. But, it looks like your slow dowm is more gravity then pressure. It could be, as you suspect, that in the down position you are blowing back to sump and not building head in the ram.
It has been my experience that when spool valves give problems it is usually because some spring loaded blow piston gets stuck in it's bore. Not having a mechanical connection to this piston makes it tough to get it free without disasembly. You can try getting the RPM up and sending some hydro hammer pressure surges through the SCV with quick and rapid movements of controls. Do it safely!
Lots of luck.
george

 

[TomG]

I do 'dipper back and boom up' quite a bit trying to keep level trench floors. I wonder if the floating boom would be helpful? I suppose the idea might work if the curl angle is set so the bucket teeth would tend to pull bucket into the ground when the dipper is pulled back. Of course, the curl angle changes with the dipper position. Always problems with these ideas.

I haven't thought of using a hoe for smoothing and compacting. I'm not sure if an example of such use comes to mind. However, the horizon of my hoe use isn't very broad.

 

[DarinRay]

Rowski,

I ran into this trouble with a different kind of backhoe but the hydraulic systems are pretty much the same. If you say that you don't have the same speed(power) in one direction it may be that the lower or upper part of the valve section has debris in the path of the dump (sump). I had to remove the power beyond plug and had sediment there but still didn't operate up to standard so I removed and disassembled the valve body sections and found more debris later in the lower dump return. Not sure if this will be your case but remove hoses first inspecting by hose fittings then in greater detail if need be. I didn't correct this matter soon enough for I ended up ruining my hydraulic pump because the relief valve couldn't relieve pressure due to the dump line debris. Hope this is of some benifit to someone.

Darin

 

[Rowski]

Re: Backhoe hydraulic problem update...

Dealer ordered me a new valve and will come up and install it as soon as it comes in. I'll update the fix and what went wrong.