Super UDT2 Hydraulic Oil

EdF

New member

Equipment
B7100HST
Apr 9, 2013
40
0
0
Jonestown, PA
When I did the last 2 hydraulic oil changes on my 91 B7100hst I used Super UDT2 oil. After both oil changes I've had problems with leaks that did not exist before the changes.

Both leaks are associate with "O" rings. First was a leak at hydraulic cylinder cap. Got that leak stopped with new O rings after 2 attempts. A second and recent leak now appears to be from O rings where the control valve attaches to the rear case cover. Hopefully this will not be a big job to replace these O rings.

My question is; was it a bad move to go with the Super UDT2 oil instead of staying with UDT as was used in this machine from new? Or, are oil leaks normal as machines age. My B7100 just turned 600 hrs so it's not like it has thousands of hours of wear on it.

Any and all comments are appreciated.
 

lugbolt

Well-known member

Equipment
ZG127S-54
Oct 15, 2015
4,807
1,575
113
Mid, South, USA
I don't know how old your tractor is, but when I got started into Kubota business in 1992, the B7100's-which at that time was all we sold-all came pre-filled with super udt. Super UDT was then superceded in the 2000's to Super UDT2. What the difference is, I can't explain, because I don't know. I remember this well because checking the oil level was nearly impossible with the shiny dipstick and crystal clear super udt; where regular UDT at that time was more of a honey colored oil, and easier to see.
 

100 td

Active member

Equipment
B21TLB (B21, TL421 & BT751) Toyota SDK4 T116 Bobcat
Aug 29, 2015
1,776
8
38
ɹǝpunuʍop
Seals deteriorate over time, it may be just a coincidence, time and wear related, meaning that the seals were going to leak at that point in time, no matter what oil you were putting in. Some folks have had more leaks when fluid type has been changed, others haven't, you may or may not experience more leaks if you go back to UDT. I don't believe UDT2 is detrimental to seals, I expect (without looking at the specs) is has a lower viscosity, so it may leak more easily than a heavier fluid, from the same point. Since it's more expensive, if you are getting benefits like lower whine etc. then it's up to you if you want to wear the cost. YMMV.
 

EdF

New member

Equipment
B7100HST
Apr 9, 2013
40
0
0
Jonestown, PA
I agree it is very hard to see the oil level with SUDT2. I use a dry paper towel and lay the dipstick on it to see where the oil level is on the stick. It's the only way I can get a good read on the oil level with these 70 year old eyes :):)
 

EdF

New member

Equipment
B7100HST
Apr 9, 2013
40
0
0
Jonestown, PA
Your comments are pretty much the same as what my now defunct Kubota dealer mechanic said many years ago. That is, switching to SUDT2 is fine because of better protection and quieter operation. I'll just have to open up the control valve, replace the O rings and hope no more leaks develop.
 

bherron1

New member
May 7, 2017
41
0
0
Clarks Hill SC USA
And full synthetic oils leak a lot easier than dyno oil or semi synthetic. They are thinner less viscosity and super slick as well as having more solvents to clean as they work. If your engine trans or gear box will hold full synthetic it is super tight and in great shape. Full synthetic shows up leaks early in anything you put it in. I just put it in a completely rebuilt engine and had to take it right back out it was leaking like crazy. I learned you must use the best gaskets and seals money can buy as well as use blue lock tight on valve covers oil pans and anything holding gaskets and seals in place. If you go back to non synthetic you will see your leak stop or at least slow down. I just replaced the oil in that engine with RP full synthetic after lock tight on every bolt and lube locker seals and gaskets. No more leaks. If you want to see how well synthetic works get two old pots on a coleman stove outside and heat the oils while reading the temps of each pot and see what happens. The dyno oil turns to grease while the full synthetic stays a clear or purple liquid and does not burn until much higher temps. If that don't convince you nothing will. I run RP full synthetic in every thing I own except an outboard motor. I'm trying to figure out if RP make HST oil. If so I want it.
 

EdF

New member

Equipment
B7100HST
Apr 9, 2013
40
0
0
Jonestown, PA
Interesting! I would switch back to UDT in a minute if that would cure the leaks. And best of all UDT is much easier on the wallet than the Super UDT2.
 

ItBmine

Well-known member

Equipment
B2620, RTV-X1100C
Jan 21, 2014
1,328
335
83
Canada
That's what I think too.....synthetic oil will clean deposits left from years of dino oil and many times you will see leaks developed.
That's why I try to only use synthetic in new stuff I can start it in right after break in.

I once switched an old garden tractor to synthetic and it started leaking out the crank seal like crazy.