Fluid in hydraulic cylinder is milky but in rest of tractor, fluid is clear.

[jgoodma1]

I have a Kubota L48 TLB. The dipper stick cylinder on the backhoe began to leak pretty badly about a month ago and today I removed it to take it to the dealer for a rebuild. I disconnected the 2 hydraulic hoses from the cylinder, knocked out the 2 pins attaching the cylinder to the backhoe dipper stick and removed the cylinder. I laid it horizontally and drained the fluid that was in the cylinder into a bucket. In the two attached photos, the first one is new fluid directly from a 2.5 gallon jug of Kubota hydraulic fluid, and the second photo is the fluid that came out of the cylinder that I'm having rebuilt. Based on other posts I've read, the milky fluid that was in the cylinder means that water was contaminating the fluid. But, I have been checking my fluid every time I use the machine (and I have been using it more than usual over the last month) and whenever I check the fluid, including today, it looks clear. Also, I had complete fluid change done at the dealer, 90 hours ago.

Today, I didn't have a good way to pull some fluid directly out of the hydraulic fluid reservoir. I could only pull out the dipstick and look at the fluid, but I did that several times, one right after the other and was able to get enough hydraulic fluid on my finger so it would drip. That fluid was definitely clear. I then took the dipstick and dipped it in the bucket with the drained, milky fluid and used the dipstick to put the same amount of fluid on my finger, as before, and that fluid definitely looked milky as it dripped down my finger. Now.....the machine is stored outside with a cover over the driver's compartment. When stored, the dipper stick cylinder faces up, so I'm thinking that with the bad seal that was leaking.....could rain be entering the cylinder at the piston seal? We have had some heavy rain over the past month. Also, I have used the backhoe for only about 10 minutes over the past month, and that was 1 week ago. Otherwise, that cylinder has been inactive. And, the day before I used the backhoe for that 10 minutes, I pressure washed the machine, and definitely squirted 2000 psi water around the piston ends of the hydraulic cylinders.

QUESTIONS:
1. Is it a mistake to use a pressure washer around the seals of the hydraulic cylinders?
2. Is it possible for the hydraulic fluid in the cylinder to be contaminated, but not the rest of the fluid in the machine?
3. With what I've described in this post, do I need to suck it up and perform a complete filters and fluid change?

Thanks!

 

[North Idaho Wolfman]

QUESTIONS:
1. Is it a mistake to use a pressure washer around the seals of the hydraulic cylinders?
2. Is it possible for the hydraulic fluid in the cylinder to be contaminated, but not the rest of the fluid in the machine?
3. With what I've described in this post, do I need to suck it up and perform a complete filters and fluid change?

Thanks!

1: You need to be very careful using a pressure washer around the seals!

2: No, it's not possible, every time you move the cylinder the fluid moves in and out.

3: Yep a full change is needed, drain all of the drains, on that model there are more drain points than on a AG tractor.

 

[Greg8352]

If you have a reserve water will be at the bottom. Does your hydraulic oil get hot enough to boil off the water.

 

[Jim Goodman]

1: You need to be very careful using a pressure washer around the seals!

2: No, it's not possible, every time you move the cylinder the fluid moves in and out.

3: Yep a full change is needed, drain all of the drains, on that model there are more drain points than on a AG tractor.

I was afraid of that[emoji36]. And thanks for the info on using the pressure washer....won’t do that again.


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[Jim Goodman]

If you have a reserve water will be at the bottom. Does your hydraulic oil get hot enough to boil off the water.

I don’t think so. I’m going to play it safe and change the fluid. Thanks.


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[Palmettokat]

Had you been running that cylinder before removing it? If so it might be air mixed into the fluid. Let the fluid set for few hours and if water will settle to the bottom it air should come out also but will not be any water at the bottom of the container.

Before I drained the fluid would remove the drain plug very slowly even holding it tight so it does not drop out of the threads, if there is water in there it is on the bottom as the water is heavier. It needs to sit over night or so but even if water is there let it drain out and some hyd oil also. Replace the plug and let it sit some longer or run it and let it sit again and do so again on the draining. You ought to be able to get the water removed doing so.

With any pressure washer I have ever run and not many, pressure right at the nozzle is strong but back up sometimes only a few inches and is not high pressure at all. Would not think you are washing it with what the solid stream nozzle. If you doubt this take a drink cup (filled partly) and while spraying begin a few feet away and see how close you have to get to blow it over.

 

[Jim Goodman]

Thanks, I’ll try that. I was using the 35 degree fan tip on the pressure washer and I was holding it back some, but I definitely came within 6” or so for several brief moments. I bought the machine used 10 years ago and in that time, have only put a couple of hundred hours on it. 3 years ago, I had the dealer replace all the hydraulic hoses on the machine, as the were starting to fail. Had a complete hydraulic fluid change done by the dealer I bought it from and the dealer who did the hose change, so I’ve not yet done one myself. When I removed the cylinder yesterday, probably 1 quart of fluid drained out when I laid it horizontally. If I do end up needing to do a fluid change, how do I make sure I get all the water-contaminated fluid drained out of the cylinders, or is the residual contaminated fluid in the cylinders not a problem once it has mixed with 5+ gallons of new fluid?


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[SidecarFlip]

Looks more like entrained air than water to me.... Easy way yo tell, let it sit for a couple days and recheck. The air will leave by then.

 

[Tornado]

I was also going to suggest it looked like Air. I am not the expert that others here are however. I know that SUDT2 fluid will look really milky when it is mixed with a lot of air. For exapmle, after changing your fluid, you will likely notice the fluid looks very milky when you first check the level. If you had a leaky seal however, and it was then exposed to rain, I would want the fluid changed. Hopefully the fluid wasn't recently changed and so you can consider it just an early maintenance.

For what its worth I have read that SUDT2 fluid handles water well. It will not separate as bad as gear oil for example. For this reason many suggest running sudt in the front axle in really cold areas where you could have the front axle freeze. The SUDT2 will not form Ice nearly as easily as the 80-90 gear oil, which will seperate from the water and leave you with a block of ice in the front axle. This is all just reading though I have no personal experience.

 

[GreensvilleJay]

re: #2 .... yes ,IF you don't fully extend and retract the ram, even then the LINES from the valve to the cylinder will have 'bad' oil in it. Say the hose is 4' long... that could be a lot of oil...

 

[jgoodma1]

When I drain the system, how to I make sure I also am able to drain all the water-contaminated fluid from all the cylinders?

 

[GreensvilleJay]

I diconnect hoses from cylinders, then pull pin on ram. manually push/pull the ram to extend/retract it. That'll push all the oil out of the cylinder.well most. You an add some fresh oil, repeat to flush out the rest.
That's the easy part.. the hard part...blocking/securing whatever 'metal' the cylinder was moving !!

You'll also have to remove hoses from valve block and drain them. low (LOW) pressure air will help purge the lines.

 

[jgoodma1]

I diconnect hoses from cylinders, then pull pin on ram. manually push/pull the ram to extend/retract it. That'll push all the oil out of the cylinder.well most. You an add some fresh oil, repeat to flush out the rest.
That's the easy part.. the hard part...blocking/securing whatever 'metal' the cylinder was moving !!

You'll also have to remove hoses from valve block and drain them. low (LOW) pressure air will help purge the lines.

Yikes! that's a lot of work and I know some of my pins will be tough to knock out. I'm more than willing to spend a $200-$300 to avoid that, so what about this idea:

1. Before I drain the machine, I retract all the cylinders as far as possible, and 1 of the 2 boom swing cylinders.
2. I remove the pin on the one extended boom swing cylinder and manually retract that rod.
3. Now, I remove the drain plug/plugs and drain the system and change the transmission and 2 hydraulic system filters.
4. I refill the system with new Kubota UDT fluid and install new filters. I operate the machine for a couple of hours
5. Now I repeat step 1 and then drain the system again.
6. I refill the system with new Kubota Super UDT2 fluid and install new filters.

If that would not be enough purging, I could perform steps 1-4 twice before moving to step 6. Would that sufficiently clean the system so I could not have do go through all the cylinder and valve and hose disconnects? I did talk to a guy at Messicks and he said I could do that, but I'd like some other feedback from you guys too.

 

[SidecarFlip]

When I drain the system, how to I make sure I also am able to drain all the water-contaminated fluid from all the cylinders?

Physically impossible to do. Will always be some fluid captured somewhere. I think you are overthinking it anyway.

Change the fluid, filters and run the thing hard, hard enough to heat up the fluid hot enough to vaporize out the water in the fluid (if any). Did you follow my advice in the first couple comments or did you just wing it?

Myself, I never get my panties in a bunch over milky looking fluid. I know that as soon as I start using my units, they will get hot enough to vaporize any entrained moisture and lots of times, it looks like but isn't moisture at all. Instead it's whipped up (by the internal transmission components) fluid and the milky look vanishes quickly.

Never worried about moisture in the fluid. I get it in the winter but it's gone first hard use in the spring.

 

[BigG]

I am going to use some number that may be off a little but they will illustrate my point.

Assume: The oil capacity of the L48 is around 15 gallons.
The amount of water entering into the cylinder is 1 oz.

15 gallons = 15 x 128 = 1920 oz of oil.

1920 oz oil + 1 oz water = 1921 total oz in the system.

Oil to water mixture of 1/1920 = .00052

Drain 10 gallons of oil (leaving 5 gallons in the cylinder etc.)

1921 - 1280 = 641 oz oil/water in the tractor. Therefore .66 oz of water has been removed assuming the oil/water are evenly mixed.

641 oz of mixed oil/water + 1280 new oil = 1920.67 oz of oil in the tractor and .33 oz of water.

Now the oil mixture ratio is .33/1920.67 = .00017

How low of a number is good enough?

 

[Bark]

Before I drained the fluid would remove the drain plug very slowly even holding it tight so it does not drop out of the threads, if there is water in there it is on the bottom as the water is heavier.

Have to do that with the tranny fluid on our AC model M. I drain into a pan until I am sure the water is out, pour that fluid into an old tall plastic juice container and let it set until the water settles than pour the good stuff back in.
Its apparently been a problem with that machine for over 80 years.

 

[jgoodma1]

I am going to use some number that may be off a little but they will illustrate my point.

Assume: The oil capacity of the L48 is around 15 gallons.
The amount of water entering into the cylinder is 1 oz.

15 gallons = 15 x 128 = 1920 oz of oil.

1920 oz oil + 1 oz water = 1921 total oz in the system.

Oil to water mixture of 1/1920 = .00052

Drain 10 gallons of oil (leaving 5 gallons in the cylinder etc.)

1921 - 1280 = 641 oz oil/water in the tractor. Therefore .66 oz of water has been removed assuming the oil/water are evenly mixed.

641 oz of mixed oil/water + 1280 new oil = 1920.67 oz of oil in the tractor and .33 oz of water.

Now the oil mixture ratio is .33/1920.67 = .00017

How low of a number is good enough?

Point taken, and I was hoping that what you're saying would be the case, that any residual fluid would be so diluted that it would not cause any problems, and that's part of the reason God invented filters. I just know next to zero about hydraulics and I just don't want to FU my tractor and be out $thousands having it fixed. I've sunk about $8000 into it since I bought it, and now I have a steering controller that has also begun leaking and that thing is $1500 for the part, and I've not been able to find any info that says it can be rebuilt, and if it could be rebuilt, who could do that. I've put around 200 hours on it since I bought it (1280 now) so $40/hour is a lot of dough for a dumb homeowner with dumb homeowner projects.

 

[jgoodma1]

Physically impossible to do. Will always be some fluid captured somewhere. I think you are overthinking it anyway.

Change the fluid, filters and run the thing hard, hard enough to heat up the fluid hot enough to vaporize out the water in the fluid (if any). Did you follow my advice in the first couple comments or did you just wing it?

Myself, I never get my panties in a bunch over milky looking fluid. I know that as soon as I start using my units, they will get hot enough to vaporize any entrained moisture and lots of times, it looks like but isn't moisture at all. Instead it's whipped up (by the internal transmission components) fluid and the milky look vanishes quickly.

Never worried about moisture in the fluid. I get it in the winter but it's gone first hard use in the spring.

The black bucket has the fluid that drained out of the cylinder 2 days ago. I tried not to stir it up when I rotated the bucket to show the white residue on the bottom of the bucket. The second photo is fluid I just now drained out of the drain plug, and it's cloudy too. I'm going to change the fluid and filters.

 

[SidecarFlip]

Have you ever worked the unit hard enough to get the fluid hot? I get mine cooking all the time and never had an entrained water issue, ever.

 

[jgoodma1]

Have you ever worked the unit hard enough to get the fluid hot? I get mine cooking all the time and never had an entrained water issue, ever.

You know....not very often. We have 11 acres, most of it wooded. Over the past couple of years, when I have time, I've been cleaning up my woods. I've been dragging deadfall out, cutting up blown over trees and then dragging or carrying the trunks out. We had some big oaks blow over in 2018 when a couple of hurricanes came closer inland than usual, and I had a couple of root balls that were about 10' tall when the trees were lying on the ground. In the last month, I trimmed away as much of the perimeter roots as I could then dug big holes and buried the stumps. I was working the backhoe for a couple or 3 hours screwing around with that, and I think the fluid got pretty hot. But no, I don't work it very hard very often. Until I posted this problem and you guys started talking about entrained water, I was not aware that condensation was such an issue with tractor hydraulics. Do you know if there some sort or retro-fit desiccant contraption out there that I could maybe add to the machine to help reduce the water accumulation?