Kubota ZD 28f Contaminated Hydraulic Fluid

[jcansler]

I have a Kubota ZD28f zero turn mower that has contaminated hydraulic fluid. Last fall while mowing the hydraulic deck lift would not lift the deck so I checked the fluid level and found the reservoir about an inch over full and the fluid was foamy on the dipstick but was a brownish gold color instead of milky looking as I have read it will be if contaminated with water.

Also the hydraulic reservoir gets very hot quickly, I guess this is from the cavitation caused by either being over filled or the fluid being contaminated.

I had checked all the fluid levels last spring and they were OK. All the fluid except the hydraulic fluid is still OK. So it seems the contamination is not coming from other fluids on the mower.

A long time kubota service manager told me to just drain the fluid, clean the screen, replace the filter and fill it with whatever fluid I wanted to use. He told me there was no need to flush the transmission as over 99% of the contaminated fluid would drain out on its own.

My question is do I need to flush the transmission by using a cheaper fluid or something else and then running the mower for a few hours then drain, change filters and then use the super UDT.

Your thoughts and advice is greatly appreciated...

Joe

 

[Bulldog]

If it was mine I would want to flush it at least once just for piece of mind. Oil is cheap compared to repair cost.

 

[jcansler]

If it was mine I would want to flush it at least once just for piece of mind. Oil is cheap compared to repair cost.

Thanks Bulldog, I was thinking that flushing would be the best way to ensure all the contaminates were cleaned out. Would you flush the transmission with a cheaper fluid or do you think it would be better to use the SUDT for the flush and refill as that is what I am planning to run in the transmission all the time? Thanks for your help...

Joe

 

[North Idaho Wolfman]

Here is the tricky part of flushing with regular hydraulic fluid, it will not mix very well with the SUDT (synthetic), so your flush would leave fluid in the system that's not 100% compatible.
This is one case where using the same SUDT fluid, albeit expensive, might be a good choice!

 

[Bulldog]

I agree with Wolfman, yes flushing with a cheap fluid would work but everything left in the system (not in the tank) will stay in the system. So then you have part cheap fluid and part SUDT. Hopefully this will be a one time flush so go ahead and bite the bullet and use the SUDT.

 

[jcansler]

Thank you for your advice, I thought flushing with SUDT would be be best way but I wanted to get others opinions before using the more expensive SUDT as a flush if there were better (cheaper) solutions. As always, I know the advice here is from experience and from knowledgeable people. Thank you guys very much for the help...

Joe

 

[rentthis]

The perfect fix is as Wolfman suggested. You might want to consider flushing with standard cheaper fluid and running the cheaper fluid until you figure out what is causing the contamination. I might be wrong, but I don't think that machine came from the factory with synthetic fluid.

 

[jcansler]

I am almost certain it came with the standard UDT not the Super. I did buy this mower new and only have 107 hours on it, at the 50 hour service interval I did change the hydraulic fluid and used the regular UDT, not the super.

As I stated, I have checked ALL the fluids on the mower and they all are on the full mark just as they were last spring when I checked it (except for the hydraulic fluid). I don't see how condensation could cause the hydraulic fluid level to be so high just a couple of months later (about 20 hours of use). Also the fluid is not milky looking, it is a brownish gold color.

Last summer I did have a theft and vandalism incident occur. A lot of the equipment that they could not carry off they vandalized and this is the only time someone could have added something to the hydraulic fluid, although if they did it is the only thing they vandalized on this mower that I can see.

Would everyone think flushing with the cheaper (slightly) Kubota UDT would be OK and would mix well when I drained this and filled with Super UDT, or should I go ahead and use the super UDT as a flush since this is what I am going to use in the end?

Also how many hours would you guys recommend running the UDT as a flush before changing it out for the Super UDT?

Thank you all for your help...

Joe

 

[Bulldog]

Unless Kubota has changed even back as far as 2000 all their tractors / equipment came factory equipped with SUDT. The reason for this was they had no idea where a tractor may end up being sold so all of them came with the better fluid so they would have the ability to handle cold weather climates.

As far as flush time, I would run it between 20 - 50 hrs unless it presented a new problem.

 

[Shadow]

I would also recommend that after your flushing is done, that you buy the transmission reservoir kit that they offer for more hydraulic fluid capacity. Alot of the 28's, especially running the 72" decks, would not have enough oil capacity to efficiently keep the hyd oil cool, and it led to hydro and charge pump failures. The kit is about $350, but that's cheaper than the hydro kit, which is closer to $1600

 

[jcansler]

Thank you all for your help. When I changed the filters and fluids at 50 hours, the dealer only carried the standard UDT not the super, so that is what I went with. The manual specs calls for using the standard UDT or the Super UDT.

From now own I am going to use the super UDT.

I may add the reservoir kit as a preventive measure. Can any of you provide a part number for the reservoir kit?

Thank you all very much for the insight and help with this issue...Take care...

Joe

 

[Shadow]

K3111-98600 is the kit number

 

[jcansler]

Thanks Shadow for the part number. I want to thank all you guys again for sharing your knowledge and helping me resolve this issue.

Once I change the fluid, filter, and clean the strainer after the flush I will be back asking questions and getting advice if the hydraulic fluid gets contaminated again. Thank you all for your help...

Joe