Changing Hydraulic Oil Question - How to purge as much of the old fluid as possible

[landrand]

I'm new to changing hydraulic oil in machinery so I thought I'd post this and do some research before I proceed.

I just changed 4 bad hydraulic hoses on the rear stabilizers on my Ford 655D backhoe. When changing the hoses, I noticed that plenty of hydraulic fluid poured out of the two cylinders. I'm getting ready to change the hydraulic fluid on the backhoe and I'm wondering if there would be any benefit to disconnecting a few other hoses on the larger cylinders to expel more hydraulic fluid so as to replace as much of the existing fluid with new fluid. I've never changed hydraulic fluid before, so any help or recommendations would be appreciated.

 

[RNeumann]

It’s a numbers game- 10 gallons on the machine and 1 gallon in the cylinders and hoses. Most folks just change the 10 gallons and leave the cylinders alone.
Same thing happens in an automatic transmission with the torque converter....

 

[Roadworthy]

To change the maximum amount of fluid without disconnecting anything be sure all hydraulic rams are fully retracted. This forces the maximum amount of fluid out of the rams and into the reservoir.

 

[nyone]

Change it 2x if your worried about it. I have water in my tractors hyd system. I let it sit(water mostly stays at the bottom) dumped it, put some kerosene in did a quick 10sec run then dumped it, then hyd oil and dumped it again....and it still looks milky. Lol

 

[bridge4]

If you replace the fluid with something other than was originally there, is there any issues usually with the stuff you don't get out mixing with new?

Thanks.

 

[RalphVa]

I doubt there are hardly any additives in hydraulic fluid to worry about compatibility. Would not think it would take very much fluid to displace what's in lines. You can easily compute how much is there by length and approximate inside diameter of the hoses. For the reservoir, I'd drain it or possibly use an oil extractor to get it empty and then use a very small amount to displace the old fluid from the hoses. Unless you've had water in the oil, I wouldn't worry about displacing what is in the hoses.

Ralph

 

[ovrszd]

To change Hyd fluid completely would require an extensive amount of labor and time. Everyone, including your friendly Dealer Shop, simply drains the reservoir, changes the filter, and refills.

 

[bridge4]

Thanks guys!