Liberty Implements Backhoe

[Boyd L]

Boyd
Temperature rise depends on amount of flow, pressure & time at pressure. What you are looking for is a noticeable difference of temperature between the pressure line going to the valve and the tank line. If the relief is opening or there is a leak in the valve stack the tank line temperature will rise vs pressure line.

Same thing with the pump, if it is slipping or bypassing internally the pump housing will get warmer than the inlet hose relatively quick.

Gauge size? I suspect this would operate at 2500 PSI or less but would recommend 3000 PSI for a little safety margin. If you have a 2500 use it. Just feather the controls to what the pressure does.

Hopefully my responses answer your questions

Your responses are most helpful.
What pressure (or other factors) can I expect the gauge to tell me? What should I be looking for?
Thanks again.

 

[oldnslo]

Boyd,
A couple of questions before answering about pressure readings.

Is the reservoir full of oil? I suspect yes since hoe is operational but check the simple stuff first.
Do hear any noises from the pump or hoe that change when a function is operating vs end of stroke?

Pressure:
This is what I would look for Since we don稚 know what the pressure is supposed to be.

Is the pressure the same for each function at end of stroke. I.e. with function stalled pressure should rise to system pressure.

If one function is 2500 PSI & another is 1000 PSI we know the pump and relief are working and have to start diagnostics on why there is such a big difference.

Does the pressure change significantly with changes of engine RPM- PTO speed?

This points towards flow loss somewhere that the heat rise tests might identify source.

My best guess is that this machine would run in the 2000 - 2500 PSI range but that is pure guesstimate on my part.

Big key in diagnosing problems is to perform tests in as logical sequence as possible before jumping to conclusions and condemning a component.

Good luck

 

[Boyd L]

Is the reservoir full of oil? I suspect yes since hoe is operational but check the simple stuff first.
Do hear any noises from the pump or hoe that change when a function is operating vs end of stroke?

The reservoir is full (FWIW I did drain and replace the fluid with new.
The only sound difference is what I suspect is pressure relief when a control is constantly engaged at the end of a stroke. Otherwise no sound difference.

Does the pressure change significantly with changes of engine RPM- PTO speed?

This points towards flow loss somewhere that the heat rise tests might identify source.

I ran the tractor for 20+ minutes @ 2500+ RPM and there was no discernible difference between the temperature of the 2 lines referenced in an earlier post.

Big key in diagnosing problems is to perform tests in as logical sequence as possible before jumping to conclusions and condemning a component.

I agree. I hope I get it right. In scouring the 'net for a pump that externally resembles this one it appears that Chief pumps have a similar configuration, provided the PTO ready splined shaft is adaptable to the Chief.

Now to get a gauge in the line feeding the valve stack from the pump.

Thanks again.

 

[oldnslo]

The reservoir is full (FWIW I did drain and replace the fluid with new.
The only sound difference is what I suspect is pressure relief when a control is constantly engaged at the end of a stroke. Otherwise no sound difference.


I ran the tractor for 20+ minutes @ 2500+ RPM and there was no discernible difference between the temperature of the 2 lines referenced in an earlier post.


I agree. I hope I get it right. In scouring the 'net for a pump that externally resembles this one it appears that Chief pumps have a similar configuration, provided the PTO ready splined shaft is adaptable to the Chief.

Now to get a gauge in the line feeding the valve stack from the pump.

Thanks again.

Did you operate any functions while running the machine? Just circulating oil I would not expect much temperature difference. Heat is created via flow loss / pressure drop through a restriction. That is why I asked to run with a function at end of stroke to build system pressure and hold there for a short period of time to see what gets warm or heats up.

Same thing with the pump test, run a function so end of stroke and them check the pump housing temperature. I expect to get a little warmer but should not get scalding hot in a short time. Usually if pump is leaking to the point that it won't build pressure it will get hot pretty quick since it is just recirculating the same oil internally.

If you are hearing the relief it does not point towards a pump problem.

 

[Boyd L]

Did you operate any functions while running the machine? Just circulating oil I would not expect much temperature difference. Heat is created via flow loss / pressure drop through a restriction. That is why I asked to run with a function at end of stroke to build system pressure and hold there for a short period of time to see what gets warm or heats up.

Sorry my response was incomplete. I ran the tractor and operated all 12 functions of the backhoe repeatedly by switching between each joystick, operating each cylinder to either its fullest extension or retraction. At either extension or retraction I held the joystick in position to cause the referenced (and hopefully correctly identified) relief of fluid.

Same thing with the pump test, run a function so end of stroke and them check the pump housing temperature. I expect to get a little warmer but should not get scalding hot in a short time. Usually if pump is leaking to the point that it won't build pressure it will get hot pretty quick since it is just recirculating the same oil internally.

The pump got a bit "warm" during this exercise but certainly not too hot to touch.

Thanks for the feedback and instruction.

 

[oldnslo]

Boyd
Until proven otherwise I do not believe your pump is the cause of the low digging force.

I am curious to see what the pressure is when you get a gauge installed.

 

[Boyd L]

Boyd
Until proven otherwise I do not believe your pump is the cause of the low digging force.

I am curious to see what the pressure is when you get a gauge installed.

After I measure and gauge the threads of the line fitting coming from the pump to the valves I plan to get to the local industrial supply house this morning to piece together enough brass/steel fittings to put a gauge in the line.
Hopefully I'll have some numbers by evening.
Thanks again.

 

[Jstpssng]

After I measure and gauge the threads of the line fitting coming from the pump to the valves I plan to get to the local industrial supply house this morning to piece together enough brass/steel fittings to put a gauge in the line.
Hopefully I'll have some numbers by evening.
Thanks again.

Just be careful when cobbling a guage together, one leak in the wrong place can be painful or even fatal. I wrecked the pump in my last bH when I hooked it up to my woodsplitter wrong, and it acted just as you describe. I took it to a hydraulic repair/supply place where they tested it... then sold me a new pump.

 

[Boyd L]

Update:
Apologies for taking so long to update progress. For the past 7 weeks I've been through a number of "experts", technicians, equipment vendors, etc....ad nauseum.
Here's what I've determined thus far, with the tractor operating at 2500 RPM the highest pressure registered was 1300 psi. That was obtained off a port on the valve stack body. I'm not certain what the operating PSI should be, but I've read on this forum (and others) that 2000-2150 seems to be the desired level of pressure.
Any useful comments?