how should I flush hydraulic fluid?

[Furu]

Furu and dfkrug,

Re: flushing the hoe. Would the method described in post #5 below work?

http://www.tractorbynet.com/forums/hydraulics/349693-how-should-i-flush-hydraulic.html#post4321224

Feel free to post in that thread.
Thanks!

I use a method that works well for me when flushing dirty or water contaminated systems. First, drain and refill, drain and refill as needed, the tractor alone, without operating any external cylinders. (In your case, that part would not be necessary) Next, remove the sump return hose from loader (or in this case backhoe) valve and drop it into a bucket. Start the tractor and cycle each cylinder system one at a time. The oil returning from cylinders and related lines will go into the bucket and not back into the tractor. Cycle each system as needed until the oil coming out looks clean then move on to the next circuit. With small tractors, fresh oil needs to be added frequently, but the end result is clean oil throughout, with a minimum of mess, and a lot less effort.

With the two hose "Power Beyond Woods mechanization" you will have 12gpm or whatever your tractor pushes coming out the hose in the bucket the second the tractor starts. As you actuate the cylinders you will get some (a little) of the old fluid out but not a lot meanwhile 12 gpm of your good fluid is going in the bucket. If you were to flush the PB circuit for 10-15 seconds you could clean/flush it out but the old fluid would still be in the lines beyond the SCV. If you then disconnected each hose at the cylinders you could actuate the SCV and wait for clean fluid After you did that twice on each cylinder (both lines) your lines and SCV would be clean. Then you still have to get the old fluid out of the cylinders. After you are done I would expect around 5-10 gals minimum of good fluid would be gone. Maybe less maybe more. It is not an simple process. That is why the dealers won't do it and most folks won't as it is either too hard or too wasteful of fluid.

Some of the posts after #5 basically say the same thing.

 

[Luke'sScreenName]

Y'all are correct. Looking at the manual (can't get to the actual hoe right now) there is only one return line coming from the valve assembly.
So I guess I'm back to manually purging the system.

Coyote, I appreciate your out of the box thinking but I forsee many obstacles arising with my level of experience around water pumps.

 

[ray66v]

Ok cool. Rubber tip seems simple. What's the rag for? What do you consider low pressure?

The rag sometimes helps keep the oil from blowing back at you.

I don't measure the pressure, but it doesn't take much. I only open the air valve a crack, so the pressure drops to almost nothing as soon as you press the trigger on the blow gun. It may only take 30 psi.

Expect sudden, rapid movement of the cylinders, which can be dangerous, depending on what they are hooked up to. And, oil spraying out of the other end.

 

[Luke'sScreenName]

The rag sometimes helps keep the oil from blowing back at you.

I don't measure the pressure, but it doesn't take much. I only open the air valve a crack, so the pressure drops to almost nothing as soon as you press the trigger on the blow gun. It may only take 30 psi.

Expect sudden, rapid movement of the cylinders, which can be dangerous, depending on what they are hooked up to. And, oil spraying out of the other end.

Ok. Thanks for the tips.

 

[Steave]

While using air pressure will work as mentioned to actuate the cylinder I'm reasonably sure it wouldn't work if the cylinder is still pinned to the stick or bucket or whatever. You just won't have enough pressure to overcome the weight of whatever the cylinder is pinned to. So now it goes back to what coyote machine had mentioned about some sort of pump. It look's as if it's boiling back down to just moving the cylinders back and forth by some means such as a come-a-long. I would like to know an easy way to do this but haven't found one so please let us know if you come across a way.

 

[Luke'sScreenName]

While using air pressure will work as mentioned to actuate the cylinder I'm reasonably sure it wouldn't work if the cylinder is still pinned to the stick or bucket or whatever. You just won't have enough pressure to overcome the weight of whatever the cylinder is pinned to. So now it goes back to what coyote machine had mentioned about some sort of pump. It look's as if it's boiling back down to just moving the cylinders back and forth by some means such as a come-a-long. I would like to know an easy way to do this but haven't found one so please let us know if you come across a way.

Ya, it's not looking good for an easy way.

And I would agree with having to unpin the cylinders.

 

[Kiotidriver]

All purging methods listed previousely seem to be a major pain to do. What about installing an in-line hydraulic return filter with the BH hydraulic return line to capture the contaminants before they return to the sump and mix with the clean HST fluid? I am contemplating just doing this. I had removed my BH before servicing my Kioti CK30 HST tractor. I drained all the old transmission fluid, replaced the two filters, and refilled the transmission with Kubota Super UDT-2 fluid (a $260 affair!). Since I need to re-install the BH on the tractor I have no choice but using the hydraulic system to do it. Unfortunatly the old fluid trapped in the hydraulic system of the BH (~ 1.5 Gal) will be re-circulated with the 8 Gallons of clean UTD-2 in the tractor. However I am hoping the in-line 10-micron filter will trap most of the contaminants. I would like to know what you guys think about this method?

 

[Luke'sScreenName]

My thoughts:
If a filter was all that was needed then our manuals would just have us replace the filters and not the fluid. Clearly the fluid degrades over time and simply filtering does not solve that. Surely, filtering is better than not... Seems like you just need to decide if diluting you new fluid by 20% is worth it.

 

[JCByrd24]

Another reason to not do filter only is that the majority of the contaminate is likely water, which a filter won't remove. If I were doing this on my tractor instead of running the the tractor to use its pump I would cut off the fuel and open the decompression lever (if available) and use the starter to pump the fluid in a much more controllable manner, with the return line in a bucket as suggested.

 

[Kiotidriver]

Well I think it is what the tractor's manufacturer assume when they set the service maintenance schedule. Most tractors are fitted with hydraulic FEL, and many are equiped with BH to. My tractor is a Kioti CK30 HST with a transmission case containing ~ 8 gallons of fluid, which can be almost all easily drainable. However the oil contained in the FEL and BH (or other hydraulic attachment) is not easly drainable and will be mixed with the new transmission oil. I think this is a situation that the manufacturers have factored in their service recommendation. Therefore if someone is doing the services as recommended, using quality lubricants this is a non-issue. Now I understand the OP had a different situation by having bought a tractor without maintenance records and having a very dirty HST fluid. In his case a drastic purge of the hydraulic system is required. For normal situation I don't think we should worry about mixing new and old fluids. But if you still worry about it, change your transmission oil and filters at half of the manufacturer's recommendation, which would be every 100 hrs on my Kioti.