Flushing backhoe attachment of bad fluid

[Dunno]

Hi,
I just picked up a backhoe attachment and saw milkshake brown hydraulic fluid coming out when I went to change the quick connects, so water in the fluid. To flush it I plan to attach the output side of tractor hydraulic lines to attachment, but leave the return line off with no quick connect on it and put in a large bucket. I’ll then start and run the tractor at low idle and cycle the backhoe while a friend adds hydraulic fluid to reservoir. How much fluid is going to come out? At full rpm, the hydraulic pump will push 21 gpm at 2750 psi. Has anyone done this? Not sure what flow will be at low rpm. How hard will the discharge be, steady stream or massive rush? I’m prepared to lose 5-10 gallons of good hydraulic fluid from machine to flush attachment. Any better ideas to flush out bad fluid? Thanks.

 

[LouNY]

You will dump a lot of fluid using that method, when ever a backhoe valve is not fully actuated you will have a straight shot of full flow. It's more work but if you have another tractor to pull and push the hoe as some one activates the controls a hose stuck in a full bucket for the supply ,and an empty bucket for what fluid comes out of the return. Physically actuating a cylinder will act as a suction pump.

 

[oldnslo]

Does this back hoe have two or three lines between tractor and the back hoe?
If three lines then you maybe can use your method since the flow should go to the power beyond port when no functions are being used and tank line would be the dirty oil from cylinders when a function is active.

If only two lines then Lou is correct you will be pumping oil out whether a function is active or not.

Flow is a function of RPM so at half throttle you would get approx half flow or around 10 GPM so lots of flow very quick.

 

[Dunno]

Hi Guys,
Thanks for the replies. There are two lines to machine. I’ll do Lou’s method. I have another machine to move hoe arm around. I think I can lift the legs myself. I ordered all the tools to do the cylinder seals, so will do those as time allows too. I kinda figured I’d end up regretting how I planned to do it, glad for your advice. Cheers.

 

[DJ54]

With the ram end disconnected, you could always use air pressure too. I did that for a loader bucket cylinder on my 480 Case when seals needed to be replaced.

 

[Dunno]

Thanks DJ,
That’s another option. How exactly is it done? Seems that disconnecting both lines from control valve would be best to get fluid from lines and cylinder. Apply pressure to each, then air to supply to purge valve. Or are hoses disconnected at cylinder, air blown into both ports to flush, then air to supply hose from tractor and operate the control valve to flush it and the hoses? Thanks.

 

[loggin]

Thanks DJ,
That’s another option. How exactly is it done? Seems that disconnecting both lines from control valve would be best to get fluid from lines and cylinder. Apply pressure to each, then air to supply to purge valve. Or are hoses disconnected at cylinder, air blown into both ports to flush, then air to supply hose from tractor and operate the control valve to flush it and the hoses? Thanks.

There are some considerations to take into account here and people will either be more concerned or less concerned about this. It has to do with how much crud is in those cylinders and lines. If your tractor is hydrostatic I would certainly want the cylinders and lines to be as clean as possible before reintroducing them to the hydraulic system within the tractor. Filters will eventually bypass if there is too much crap and hydrostatic pumps are not cheap. Just sayin..

Is this a 3 point hitch type backhoe or an on frame type? Is the tractor hydrostatic or not? What model tractor?

I suppose you could always attach a pto driven hydraulic pump and separate reservoir for the backhoe and keep the whole system separate and that way you would at least not influence the rest of the machine.

Just some things to consider while getting it all flushed out.

 

[Dunno]

Loggin,
It’s a skid steer I use around the farm, so hydrostatic, which is why I’d like it as clean as possible. The backhoe attaches to the frame of the skid steer. I will mount it using one of my tractors, which I’ll use to cycle the arms if I use that method. I’m thinking air pressure might be easiest. Thanks.

 

[DJ54]

Thanks DJ,
That’s another option. How exactly is it done? Seems that disconnecting both lines from control valve would be best to get fluid from lines and cylinder. Apply pressure to each, then air to supply to purge valve. Or are hoses disconnected at cylinder, air blown into both ports to flush, then air to supply hose from tractor and operate the control valve to flush it and the hoses? Thanks.

I just wanted to get oil out of the cylinder quickly, it was not contaminated. I made an adapter from the JIC fitting to pipe, then adapted to 1/4" for a quick connect to air supply. With ram disconnected it doesn't take much air pressure to move the ram to push oil out, but seems I set the regulator on the compressor to around 15-20 psi. I had a couple spare 1/4" ball valves, so ran a male quick connect air fitting to one side and adapted to JIC to NPT adapter for air flow control so it wouldn't blast oil out into a bucket. I just happened to have enough "stuff" on hand to do that.

Being it is for a skid steer I assume you have 2 hoses connecting to skid steer. You could adapt air to the pressure side, remove hydraulic quick connect from the return side to push into a bucket/container. With the rams disconnected you could use the control valve to purge which cylinder you want to purge.

Once the initial purge is done, being it's contaminated with water you could remove adapter pour some 90% rubbing alcohol in the hose, then cycle. It should pick up any remaining moisture in the cylinder. Then repeat with hydraulic oil, then just air alone for a final purge. Time consuming yes, but less expensive than a bucket or two of hydraulic fluid.

If it were me and planning on rebuilding the cylinders, now would be the time. At least you know you'd be starting with a clean system, especially using the alcohol, or alcohol/hyd. fluid mix to clean the control valve. Alcohol won't be in there long enough to damage any o-rings. JMO...

 

[Dunno]

DJ,
Thank you for the detailed how-to. That will be useful to a lot of folks. I didn’t know about the alcohol part, great info. I bought SeaFoam if I remember to flush the power steering system of my ‘61 Ford industrial 4000 (which I haven’t done yet), and the alcohol will do the same here. Thanks again!