Backhoe blowing hoses

[pinus]

Guys, I have a rhino backhoe on a 30 horse Kioti tractor. The backhoe has an external pto pump/reservoir. This weekend while using it to dig a trench for a friends outdoor furnace lines I blew line after line. Lets see...I blew 6-7 lines in the 2 days and 75 feet of digging. Both lines on the boom lift, the larger line from the pump to the levers twice, and my brain is tired and can't remember the rest...

This backhoe is a 2003 model and some of the places have some wear and I've blown hoses in the past but good gosh nothing like this.

My only changes recently is that I changed the fluid and filter. When I did this, I put hydraulic fluid back into it instead of the motor oil that is recommended.

Any thoughts of what is going on here? It was some pretty tough digging on better than 1/2. Frozen surface ground and heavy clays.

Maybe some problems with to much pressure, a valve malfunctioning? I'm into a area I know nothing about so any help would be greatly appreciated.

Thanks,

Brad

 

[beenthere]

Have you checked any of the oil pressures with a guage?

And why the hyd. fluid instead of the motor oil recommended ? Maybe the relief system malfunctions with hyd. fluid, but know of no reason why.

Did you bury all the oil along with the furnace lines?

Did you have to pound your way through the frozen clay?

Did the lines break on the curl cyl. ?

 

[Ford tractor]

For some reason, you have too much pressure (assuming you didn't get low pressure hoses!). Check the pressure and adjust the relief valves to get it to spec.

Q: did it blow lifting the boom or dropping it? There can be a relief valve to protect against over pressure when dropping the boom where gravity is your enemy.

 

[pinus]

It always blew when I was either curling the bucket or lifting the entire arm. I didn't pound per say since the backhoe never has been that "active" or function like a "real" backhoe might be a better word.

That is partly why I went with hydraulic fluid, my reasoning being that some of the later models are working off the internal hydraulics of the tractor and I was hoping it would give it a little more power.

It did not always blow a line in tough conditions. There was at least 2-3 blown while in good digging but thats not to say I didn't stress them I guess.

Sounds like I may need to find a way to check pressures.

 

[J_J]

It soesn't seem logical to be blowing hoses with an external PTO pump, as the most common ones only have about 2000 psi. Although you might have another kind of PTO pump with a pressure upward of 3000 psi. I would suggest age, wear and tear and cold perhaps. Dynamic pressure caused by ram effect could burst some hose. Does the BH valve have work port reliefs?

Are you using any QD's with the BH?

Install a pressure gage and check the PRV for the BH.

 

[wvpolekat]

My only changes recently is that I changed the fluid and filter. When I did this, I put hydraulic fluid back into it instead of the motor oil that is recommended.

There is your answer. Drain/flush it and put the correct fluid in it.

 

[Mace Canute]

There is your answer. Drain/flush it and put the correct fluid in it.

Please explain exactly why you think that has to be the problem.

 

[JFS2295]

My ARPS BH specs motor oil but for 25 years I've used NH 134. Only time I have a hose leak is from rubbing wear or damaging the hose on trees.

 

[wvpolekat]

Please explain exactly why you think that has to be the problem.

Let's change the wording around some.

I put gasoline in my tractor instead of the diesel it specifies, now it won't run.
I put ATF in my engine instead of motor oil, now it knocks.
I put water in my radiator instead of coolant, now the water pump seized.
I put non-HE soap in my HE washing machine, now I have suds everywhere.
I put 90w in my automatic transmission instead of ATF, now it won't go.

Nobody would even blink an eye at someone telling them they put the wrong fluid in and that caused the problem. The system is speced for motor oil and he put something else in it, suddenly it's blowing hoses. Deduction tells us that if nothing else changed, that is the most likely cause. May be not directly, but it could have freed some trash up and clogged the PRV or something similar. But, the likelyhood that something unrelated went wrong after putting the incorrect fluid in it is slim to none. If nothing else, getting the system back to how it was intended to operate would be a wise first step.

 

[Jay4200]

Maybe some problems with to much pressure, a valve malfunctioning? I'm into a area I know nothing about so any help would be greatly appreciated

The control valve has a relief on it that blows off whenever a function hits a stop. If your relief valve is malfunctioning and isn't opening, then you will generate full dead-head pump pressure at the end of every stroke, not to mention if you overstress while digging. That sounds like your problem.

The other issue, which is related, is if the viscosity of the new hydraulic fluid is higher than the recommended motor oil, then the system could generate higher than normal internal pressures even with the relief blowing off.

JayC

 

[Mace Canute]

Ok, if you say so...

I would think a person would need to have more information before averring that was the problem considering the OP has said nothing about the viscosity of either, which would have the most effect.

 

[wvpolekat]

Ok, if you say so...

I would think a person would need to have more information before averring that was the problem considering the OP has said nothing about the viscosity of either, which would have the most effect.

If you want to advocate randomly swapping fluids and then acting like it couldn't have caused problems that occur immediately afterwords, that's your choice. Next time you change your oil, why don't you try washer fluid instead, it's a lot cheaper. Or, since you obviously think that motor oil and hyd oil interchange, try using it. Let us know how that works out for ya, ok?

Basically ignoring the fact that he openly said he put the wrong fluid in it just before this problem started is foolish. I think you know this, but for some reason want to take me to task on my pointing out what I feel is the most obvious thing in his entire post. No skin off my nose, just don't come anywhere anything of mine that has fluids in it.

 

[J_J]

I believe that Parker hose and others is burst tested to 4X max. Just don't think the pump can build up that much pressure. The control valve probably has a pressure rating somewhere around 3000 to 3500 psi. Dynamic pressure can exceed 5000 psi when a ram is forced by mechanical action. Did you ever blow out a return hose? Check them QD's if in use.

 

[Ford tractor]

Ok, if you say so...

I would think a person would need to have more information before averring that was the problem considering the OP has said nothing about the viscosity of either, which would have the most effect.

True, but it's likely that the original spec was 5w30 and straight weight hydraulic fluid will be 30 to 40 wt equivalent. Possibly higher. It would be
nice if the OP could chime in with the specs for the original motor oil and the exact hydraulic fluid used.

Don't forget that straight weight gets thick MUCH faster than multi-vis motor oil. In the olden days, it was common to add 1 gallon of kero to 4gal of hydraulic fluid in the winter to thin it out.

And yes, different viscosity fluid can change the system pressure due to he reactivity of the relief. More food for thought.

 

[wvpolekat]

I believe that Parker hose and others is burst tested to 4X max. Just don't think the pump can build up that much pressure. The control valve probably has a pressure rating somewhere around 3000 to 3500 psi. Dynamic pressure can exceed 5000 psi when a ram is forced by mechanical action. Did you ever blow out a return hose? Check them QD's if in use.

Bad batch of hose? Badly made hoses?

 

[Jeff Lary]

I agree if it were me i would at least try using Motor Oil like you said it was supposed to have. I might go to wall mart buy cheep motor oil at first and try it, if it seems to work fine then i would drain the cheep and refill with a better grade of oil. That way if you keep blowing hoses it would not be the better grade of oil and if it works, well you are helping to flush the system of the Hyd oil when you replace it with the better grade. Good luck

 

[Mace Canute]

True, but it's likely that the original spec was 5w30 and straight weight hydraulic fluid will be 30 to 40 wt equivalent. Possibly higher. It would be
nice if the OP could chime in with the specs for the original motor oil and the exact hydraulic fluid used.

Don't forget that straight weight gets thick MUCH faster than multi-vis motor oil. In the olden days, it was common to add 1 gallon of kero to 4gal of hydraulic fluid in the winter to thin it out.

And yes, different viscosity fluid can change the system pressure due to he reactivity of the relief. More food for thought.

Exactly! Without knowing what the respective specs are, it's premature to say the hydraulic oil has too high a viscosity. It might very well have an equal or lower viscosity.

 

[pinus]

Guys, I really appreciate the feedback and points made. I should have provided some specs first. Here are some of the details in the manual:

Operating Pressure: 2150 psi
Bucket Digging Force: 2875 lbs.
Dipperstick Digging Force: 1744 lbs.
Oil: 10W40 engine oil with API "SD" classification in Northern climates, SAE 40W in Southern Climates. (I'm in southern Missouri)

I stopped at a local logging equipment shop today to have a new supply hose made. They seemed to think it was a stuck pressure valve...not sure if that is stuck shut or stuck open. Looking at the illustrations in my manual it shows what they call relief cartridges which are non-repairable except for seals...is this what they are speaking of.

Don't mind switching the fluid and filter back as discussed. At least I understand how to do this!

 

[ptexer]

It sounds like some tough digging. Once on my JD 310 I had multiple hoses blowing. I resecured all my hoses to reduce vibration and that fixed my problem.

 

[wrenchturner]

Pressure relief valve has to be sticking. Seen it happen on automobiles.