Cleaning/flushing hydraulics

[rdobb13]

Had a friend ask me the best way to clean or flush a hydraulic system.  He recently bought a mustang skidsteer that the pump was supposedly out.  When the seller started it and let it warm up all the hydraulics worked.  Once he got it home after start up it is sluggish and the tilt won't work, when it warms up all is good until an hour of use and then it fades.  He said fluid is milky and has debris in it.  Any good home remedies?  Also something I've considered doing to my stuff once I get it home.

[BargeMonkey]

 I would drain the entire system, clean the hydraulic strainer if it has one and change any filters in the system. Fill it back up, run for a few hours till it got hot and dump it again. A pump on a skidsteer can be enough of a pain, you start chasing debris in any system it gets costly. Having someone who knows pumps / good mechanic look at it would be worth while, it may have just enough water / sludge / debris that if you catch it now your pump isn't completely shot.

[submarinesailor]

If I were going to do it, this is what I would do:
1.   The very first thing would be to position the skidsteer so that the drain on the tank is on the downhill side.
2.   Start the tank draining.  Leave drain open for a while after the oil is done running out.  Hopefully this will allow some additional water to drain.
3.   While it tank is draining, change the filter.  NOTE:  That this stage the oil and filter can be just any cheap ones that meet the manufactures requirements.
4.   Refill with the cheap stuff making sure the tank fill is closed.
5.   Try to perform about 30 minutes to an hour worth of work.  This will heat the oil, allowing the remaining old and new to mix.
6.   Perform 1 thru 5 again.

Now here's where things get opinionated.  Again if I was doing it, I would perform 1-5 a second time with using a cheap oil and filter. 
But if the money or opinion isn't there......After draining the oil the second time.  Go ahead and fill with one of the better oils out.  Again opinion time:  I would use a synthetic hydraulic/transfer fluid: Chevron, Mobil, Valvoline, Shell, AMSOIL..i.e.  Why synthetic?  Because most of them have better hydroscopic characteristics than the mineral oils do – they deal with water much better.
If the money is there, perform 1-5 a second time filling with a good oil/fluid.

Why 3 times?????  This really lowers the amount of water in the system.

Two more things for you and him may want to think about: 
1.   If possible, flush out the tank.  I would use a garden sprayer if you can.  If the tank can drain really well. Use something cheap like Simple Green and wash the hell out of it.  If not, use some diesel fuel or Kerosene, remembering to drain it really well.
2.   After the flush and refill are done, make sure the system is as closed up as tgiht you can get it while making sure you allow for expansion and contraction of the oil.  The tank/system should have a breather on it somewhere which I recommend a desiccant breather, http://descase.com/breathers, be placed on it.  These make a HUGE difference in the amount of water that gets into the hydraulic systems.

Bruce 

[rdobb13]

Thanks guys.  Showed him this and he asked if cycling diesel through the system was a bad idea?  Again, I had no answer to give.  Pretty sure kerosene is a bad idea, diesel?

[submarinesailor]

In my opinion it is a very bad idea.  Both of them do not have the viscosity needed to protect the pump.  I believe parts of the pump could rub together during the flush.  Also, you don't know if the software is compatible with them.

Bruce

[danreed76]

In my opinion it is a very bad idea.  Both of them do not have the viscosity needed to protect the pump.  I believe parts of the pump could rub together during the flush.  Also, you don't know if the software is compatible with them.

Definitely agree with this point, diesel and kerosene can turn incompatible rubber (including all your hose liners) into a spongy gel... then you have serious issues.  Also the lubricity is not there to protect your bearings/seals/swash plates, etc.  (I will add that since I left the boat XX years ago, people look at me like I have two noses when I refer to "software".)

I would go with Bruce's recommendations with a couple of added suggestions:
1.  Warm the hydraulic system up and cycle all the hydraulic components several times prior to draining, to ensure the water is suspended in the oil.  Make sure you drain it from the lowest point in the system (on mine there's a drain plug in the suction cavity of the pump).
2.  When you clean the tank, take the time to clean the internal strainer if it has one and use lint free rags (tee-shirts are perfect for this, never terrycloth or towels) and an evaporating cleaner for the final cleaning (brake cleaner, Lectri-kleen, etc) and let it dry completely before putting hydraulic fluid back in.
3.  Many skid steers have a semi-pressurized return, meaning that instead of a traditional breather, it's more like a radiator cap.  It maintains the system under a 3-5 psi pressure on the tank to keep water and contaminants out.  If that's the case, make sure it has the correct cap and that it is maintaining a positive pressure on the tank.  Often these get changed out for a breather type cap when the cap gets damaged or lost.  On my ASV, this contributed to a lot of pump noise (the previous owner had a breather on it).
4.  Verify the proper fluid is being used (find out what the manufacturer's spec is).  Many newer machines are very finicky about the viscosity of the fluid.  These are close tolerance pumps and valves; if the fluid is getting too thin at operating temperature, it can cause performance issues.  Many machines require a high quality multi-vis fluid to have proper operation through all temperature ranges.  The sluggish-to-good-to-fading operation sounds a lot like a fluid viscosity issue.  I've seen this with both skid steers and hydrostatic tractors.  Cold the fluid will be too thick, then it's just right for a while, then too thin when it's hot.  For example, my machine lists an Eaton specification and a Rexroth specification... I look for that on the label of my hydraulic fluid.
5.  Consider cutting open the old filters and make note of any metal or debris (same with the suction strainer and tank inspection).  This will help tell you if the pump is on borrowed time.
6.  When you go to run the machine during the flush, take several opportunities to cycle the cylinders (boom and bucket) to their full stroke, all the way up and down.

It's not unusual to find a machine that someone thinks is failing and end up with a perfectly good unit that just needed some attention to detail.  Hope your friend has some good results!

-Dan

[rdobb13]

Someday you guys are gonna teach me enough that I may become helpful.  I appreciate all the knowledge guys.

[submarinesailor]

I don't think you have one lying around.  But if you have a small ultrasonic parts cleaner, I would use it to clean the "internal strainer(s)".  Several times we had heavy duty problems with various types of strainers with different mesh sizes.  The normal thing to do was to replace them from the supply system.  About 60% of the time there weren't any in the system.  So we used the small "UT" cleaners with 190 proof grain alcohol (Everclear) as the cleaning agent.  I can't remember one that the alcohol and UT cleaner did not clean.

I know the Tiger Team from Charleston Naval Shipyard used it on MANY strainers when one of the boats did something really STUPID and ended up with NO hydraulics.  Sitting on the surface waiting for an ocean going tug to come get them.

Bruce

[danreed76]

Just another quick thought.... might be worth draining a sample of the hydraulic oil into a bottle or jar while draining, let it settle and make sure the milkiness is due to water contamination.  Any free water should settle to the bottom, and air bubbles rise to the top.  I had an old backhoe that got quite milky due to a leak in the suction hose.  Never dripped any fluid but sucked air in and made the fluid look milky.

If it's for sure water in the system, it may be worth taking a look at the oil in the drive boxes (chain boxes) to see what condition it's in.  There's a number of ways for skid steers to get water in them... if you're not sure how the water got in there, there may be water other places it doesn't belong.

Quick edit:  To a couple of Bruce's points above; the UT cleaner is an excellent tool to have for the strainer, especially considering you already have evidence of debris.  Also, if you can find a synthetic oil that meets Mustang's specs, that may buy some extra time if the pump is suspect.

Dan