Backhoe hydraulics issues

[mscher]

I have recently aquired a 69' Ford 4500 backhoe.

The bucket will lift upwards (forward) and down to about 90 degrees, no problem. any further back and it just stops.

The swing arm hydros (2 using a swing chain) moves good, but will only travel from about 10-2 o'clock. It can be moved the rest of the way by hand.

In both cases, there is no strain on the hydro pump. Things just stop.

The rest of the backhoe hyraulics, seem to work pretty well.

Any help appreciated.

 

[rbh]

Re: Backhoe hydraulics issues

can you here the pump cavitating??? (low fluid level)

I do not know were all your rams should be fully in or out or halfway when you check the fluid, you should look into that, as well when you check it cold remember it will expand, do not over fill.

(other things to look into, collapsed or pinched lines, pluged or partially pluged filters, pumps on its way out)

 

[puddle jumper]

Re: Backhoe hydraulics issues

All of your hydraulics's should be fully retracted when checking the level. Something to check would be that all of the lines have been blead of air.

 

[Pascal]

Re: Backhoe hydraulics issues

I'm not sure exactly which circuit you are referring to besides the swing. If you could post a more specific picture of both setups it might be helpful.

Until then, first check the fluid level as suggested then look at the outside of the hydraulic cylinders for damage that would transfer to the inside and damage the piston seals. Leakage past those seals could be a cause of what you describe as could a relief valve setting that has worn away to a lower value.

There are a few other possible causes as well but that can wait till later.

 

[mscher]

Re: Backhoe hydraulics issues

I'm not sure exactly which circuit you are referring to besides the swing. If you could post a more specific picture of both setups it might be helpful.

Until then, first check the fluid level as suggested then look at the outside of the hydraulic cylinders for damage that would transfer to the inside and damage the piston seals. Leakage past those seals could be a cause of what you describe as could a relief valve setting that has worn away to a lower value.

There are a few other possible causes as well but that can wait till later.

Don't have an image, but it's the one cylinder that moves the digging bucket.

I have never ran a backhoe, but it looks like this bucket should travel from about 1 o'clock, to about 8 or 9 o'clock. It moves fine, between 1 and 3 o'clock and then just stops, with no strain on the pump.

The previous owner had the cylinder re-done, with the exact same results.

 

[Summer Fun]

Re: Backhoe hydraulics issues

There should be 2 holes on the back of the bucket

Put your ram on the top hole and you'll get full travel from it. .

 

[mscher]

Re: Backhoe hydraulics issues

There should be 2 holes on the back of the bucket

Put your ram on the top hole and you'll get full travel from it. .

Interesting, but it has the same setup, since it has been new.

The hydraulic cylinder is only retracting about 1/2 the way in.

I will try it though.

 

[Bob_VT]

Re: Backhoe hydraulics issues

Wracking my brain...... I am sure there are valve adjustments in or on the hydraulic control box. It controls the line pressure. I had a mechanic open them all the way up on a backhoe I used to operate to give it more power. It was a dramatic improvement.

Without having the unit where I can see and feel it that would be my best guess since the previous owner had the same issue after a cylinder rebuild

 

[Pascal]

Re: Backhoe hydraulics issues

Don't have an image, but it's the one cylinder that moves the digging bucket.

I have never ran a backhoe, but it looks like this bucket should travel from about 1 o'clock, to about 8 or 9 o'clock. It moves fine, between 1 and 3 o'clock and then just stops, with no strain on the pump.

The previous owner had the cylinder re-done, with the exact same results.

Since the previous owner had the bucket cylinder re-done, I can only suggest that there might be a problem in the cylinder that the tech didn't find. That might be what is called an expanded barrel but ignore that for the time being

Given the sissor links on the bucket, would there be excess wear on any of the pivot points that might generate interference?

You did say that there was "strain on the pump" so that tells me that either the system relief valve is set very low (weakened spring over time) or there is oil bypassing somewhere at a point that pressure builds to the that resistance.

There is a main relief valve that should be in the loader control valve.

There are circuit relief valves in the individual circuits. Sometimes these have junk stuck in them that allows leaks and there are O-rings that deteriorate over time as well.

If all the circuits are slow as well, there is likely an adapter in the outlet of the loadercontrol valve called the 'powerbeyond'. If the o-ring in that adapter is damaged, it will allow oil to leak back to the reservoir before it even reaches the backhoe valve stack.

So far as the swing function performance is concerned, in addition to the above, I would look for binding in the chains, interference between the chain and sprocket due to wear and cylinder problems, mounting and internal leakage.

 

[Summer Fun]

Re: Backhoe hydraulics issues

The hydraulic cylinder is only retracting about 1/2 the way in.

I'll bet the rebuilt cylinder was rebuilt wrong.

It wouldn't be the first time one came back screwed up. :facepalm:

 

[Pascal]

Re: Backhoe hydraulics issues

I'll bet the rebuilt cylinder was rebuilt wrong.

It wouldn't be to first time one came back screwed up. :facepalm:

It is possible. There is a way to test the cylinder without taking it apart.

 

[Summer Fun]

Re: Backhoe hydraulics issues

Well mscher whats up with it ??

 

[mscher]

Re: Backhoe hydraulics issues

Well, my own personal mechanic (my brother) has it working much better.

The swing had some type of limiter switches that needed adjustment. Much better. He suspects that the bucket problems, are coming from the control valves. He had it moving much furthur, but it does not have the power. Not sure if he has had time to check into it furthur and I have been swamped at work. The control levers are all very sloppy, also, so they will need some bushings, etc.

That backhoe will be a ferocious digging beast, when we get through with it. Can't wait.