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!

 

[DJ54]

I learned about the alcohol about 15 years ago. A fellow on another forum mixed 50/50/ diesel and ATF plus 1 Qt. of rubbing alcohol to flush a transmission on a tractor. I'd bought an old Case backhoe that the transmission oil looked like a yellow milkshake. Put the above mix in and drove it around for 10 minutes and immediately drained it. I had to pull the shift cover off to fix the shifter and could not believe how well it cleaned it up.

Did the same on my little 140 Farmall 4 years ago. PTO bearings were shot due to water in the transmission/differential. Picture below is how well it cleaned it up and removed all the moisture. Mopped out what was left in the bottom with shop rags.

 

[Dunno]

Great pic! Really did clean it up. I’d do the seals on the cylinders that need them along with the flush but have some fruit trees that need to go in the ground this weekend, so I’ll have to wait on that. While we’re at it, I need to free up a frozen rear brake on an old Ford F600. I don’t want to beat on it too much for fear of cracking the hub so I plan to pull the massive thing off the axle and set it in a small tub of homemade pb blaster, which is 1:1 atf and acetone. Thanks again for the great info.

 

[DJ54]

Welcome...

 

[Dunno]

I have hit a snag. I was able to extend the dipper, but cannot get the crowd/boom cylinder to move. I have the hoses disconnected from the control valve in order to let the fluid out, but it is not moving. As you can see in the picture, the weight of the hoe frame mount is in the air whereas you’d think that its weight should be way more than enough to pull the cylinder open. Two thoughts are seized pin on which it is mounted to, or seized cylinder rod. Anyone have any ideas what to try next? Thanks.
PS I spoke to the previous owner and he said it all moved freely for him.

 

[dfkrug]

I have hit a snag. I was able to extend the dipper, but cannot get the crowd/boom cylinder to move. I have the hoses disconnected from the control valve in order to let the fluid out, but it is not moving.

Since you have removed hoses at the valve, try some air. You can just use your airgun with 125psi pressure from your compressor. Movement using air can be sudden, so be careful.

I have used air to clear fluid before, but I prefer to remove as much oil as possible from the cylinders by externally articulating each cylinder, using another machine (tractor, forklift, or hoist). You have to hold the appropriate valve open, plus disconnect the valve return hose and place in a bucket.

 

[Dunno]

Hi DK,
I took you advice and did this earlier. I was able to extend the dipper by lifting and actuating the lever, and it worked. Tried same procedure on boom, but no joy. Will try the air on the line tomorrow. I also found out that half of the cylinders leak. I don’t mind a drip or two, but this thing leaks pretty good, so time to reseal them while I’m at it. I’ll be digging the tree holes the old fashioned way, but hey, good exercise. Thanks for your help.

 

[Dunno]

We’ll, I tried air pressure to the disconnected lines and still no opening of the rod. The rod did move ever so slightly with air to both lines one at a time due to the play between rod eye and lower pin, so I don’t think the rod is seized in the bore. Leads me to think there is either a jam or seizure of the bottom boom pin. PO said it cycled for him, so I’ll take his word on it for now. Anyone have an idea of what could be holding the frame up in the air? I’m hoping I’ve over looked something. It is a Bradco 11HD rebranded by Gehl, so a pretty common piece of gear. Thanks,

 

[LouNY]

I'm sure that you have checked but does it have a "transport" lock or pin?

 

[Dunno]

Yes. Not locked. Thanks. FWIW, one of the stabilizer legs is still up after cycling the lever with no quick connects on hoses. I thought gravity would pull that down too.

 

[DJ54]

Am I reading right that you didn't remove the pin from the ram end..?? Note I did say I purged my cylinder with pin removed. Depending on your compressors max. PSI, the best you'll get in force is psi X cylinder ID and not nearly enough to move much if still fully connected.

Most newer tractor hydraulic systems will push approx. 2500+ psi X the ID of cylinder makes a huge difference. Since you need to rebuild the cylinders before using, you'll need to disconnect the ram end to do it, using air now to purge cylinders would make it a lot less messy.

I have no idea what type of gland nut the cylinders have on them but found on my old Case 480C it's easier to rebuild in place, and not remove. The gland nuts on it need to be torqued to 400+ ft, lbs. so leaving it pinned on the hoe was the best way to hold it.

If you've never rebuilt a cylinder, I highly suggest getting a set of the internal seal tools that collapse the internal seal to install. Makes it so much easier..!! Didn't even know they made such a thing when I did my first one. Got mine off Amazon.

I rebuilt one of the swing cylinders on my 480 last Fall and found the piston bolt needed to be torqued to 400+ ft. lbs. too. Easy to do with my impact wrench and used the Permatex "orange" thread locker. I have a buddy who is a heavy eq. mechanic for a local dealer, and he told me that's what they use. Good enough for them, good enough for my old Case.