Milky hydraulic fluid

[mobile demensia]

My used mill I recently purchased had a leak at the top of the hydraulic tank that let rain water in. I drained all the fluid from the tank, most of the hoses and all of the cylinders. After filling the tank with new oil I started the mill up and ran through all the hydraulic functions. Everything works great but my fluid is cloudy again. Any ideas on the best way to clean my hydraulic system without changing the fluid so many times it breaks the bank. It is an open center system as far as I know. There were a few hoses that were hard to get at and I did not drain the valve bank. Thanks for any info.

MD

[trim4u2nv]

I had this happen on an electric over hydraulic tailgate.  It was small enough to remove the tank and freeze the contents in my beer cooler.  Just pulled the chunk of ice out several times (freeze/thaw) and this did the trick.  If it wasnt really expensive synthetic oil I would have just changed the fluid.

[mobile demensia]

When you freeze water emulsified in oil does it separate?

[trim4u2nv]

I have had it separate in atf and synthethic hydraulic fluid.   Put it in a 5 gallon bucket and the oil will float on top.  I know it will freeze because the hydraulic cylinder was stuck in the up position until we brought the vehicle into a heated garage.  It also cracked the vane in a pump that used atf when frozen solid with water contamination.  I would be more concerned with rust at this point. 

[mobile demensia]

I will take some oil out tomarrow and put it in the freezer to see if this is the cure. Thanks

[beenthere]

When it gets to the point that the water is emulsified with the hyd. oil, seems freezing wouldn't work. Will be interested to see if any experiments are successful.
If the water does freeze, will it be just some very small crystals, or thinking it will be a block of some larger size that will appear? Interesting, to say the least.

Before it becomes emulsified, then the free water would float on top, and freeze as well as cause rust.

[trim4u2nv]

We have had sucess with many cycles of freezing and thawing.   In fact in chicago you can set a bucket by the garage door in the winter and after a month you can see a big chunk of ice form.  I use this for chainsaw bar oil.  On really big systems you can use vacuum distillation on a sealed tank 1 atm vacuum and heat to around 133 fahrenheit. to boil off the water.   Or dehumidification in the airspace above the fluid.  I have seen top reservoir venting on  of hydraulic car crushers for that purpose.  They just blow very dry air over the top of the fluid to draw out the moisture.   I wouldn't do any external heating as most hydraulic fluid is mineral oil and will flash (fire up) pretty easily.  (grew up near whiting amoco oil refinery)

[bandmiller2]

MD,hydraulic and most fuel tanks don't drain small amounts of water off the bottom of the tank.If your unit has a hydraulic fluid filter, change it once or twice,if not install one [return side].Outher way is get it hot and redrain everything.You could try letting the water separate, eventually it will.A partner of mine had an old Kubota, there was a minor amount of water in the steering box below the drain plug, and would lock up the box in the winter.I put a teaspoon of gas line antifreeze [methanol]in the box no more lockups.Wile we're on the subject I used to get 55 gallon drums of diesel fuel with entrained water, free.I would let them settle and after a real cold spell filter it through several layers of skivie shorts,only problem the shorts were itchy after. Frank C.

[Corley5]

My old Iron Mule used to get milky hydraulic fluid on occasion for whatever reason.  I'd add Sea Foam Trans Tune to the system and run it.  Between the additive and the heat produced by the system the milkiness would go away 

[NCDiesel]

While I have a manual mill, I have used and operated a lot of hydraulic equipment.  As others have mentioned freezing/settling will not work for entrained or emulsified water.  Two flushes and filter changes  is the standard fix for this.   I am not sure how hot the hydraulics get, but as others have mentioned trans tune after the second drain and then really working the system will usually finish up the job if the oil gets hot.

Be sure to put an hour on the system before the second drain to ensure you have completely mixed residual oil with the new oil.

PS:  Break open the hose connectors and use compressed air to blow residual oil back (be safe when doing this and be careful to not add your own airborne contaminants of course) to the tank where possible when draining the second time.

[mobile demensia]

I did a little experimenting today with heating some hydraulic oil and boiling the water off. It worked on a small scale. My wife, who has lots of experience cooking and with deep fryers, told me the oil will not go past 212 until the water boils off. So will bringing the oil up to 220 degrees ruin the oil?

[bandmiller2]

MD,you didn't say if you had a filter in the system,if not I would add one. all filters will remove water some are designed to do it better.I wouldn't bother to cook the oil,with just a little moisture in the system use the mill get the oil hot and have the tank vented good,the moisture will evaporate. Frank C.

[mobile demensia]

I do have a filter in my system and I looked at adding a water absorbing filter to remove the water. The only reason I didn't is it cost half the price of a new bucket of oil and I had no idea if it would do the job. I ordered a new bucket of oil but before I changed it again I did a few hours of milling and it looked as if the water was evaporating off. I will see is this continues, I may just keep this new bucket on standby.