M59 hydraulics got slow and weak.

[rScotty]

OK, I pulled some samples from my own tractor yesterday. Temperature here is in the 70s, trans/hydraulic oil is New Holland Multi-G 134 with 100 hrs on it which included all new filters. Only hydraulic problem we have is a bit of whine from the high pressure pump (on engine right side) when the motor is cold.....which either goes away or gets so quiet I can no longer hear it as the machine warms up. This M59 rarely gets asked to do much hard work and definitely not quickly. It's babied.

I took a picture before starting the tractor and the oil is clear. Any haziness is simply whatever was last in that syringe.... The second sample is about ten minutes later after using the backhoe to lift and load a table saw into my buddy Craig's pickup. Altogether the M59 ran at idle for about ten minutes, moved the backhoe booms twice rather slowly, and drove about 50 feet in low gear.

We were flabbergasted at the amount of bubbles of entrained gas (air? oil vapor?) in the oil. Craig and I both know a bit about the physics of air and vapor entrainment in fluids....it would be interesting to know which type this is. Whichever it is, we were sure surprised to see it there. To make sure, I drew another sample and it was identical. The sample in the photo has been in the syringe less than a minute and looks to be already clearing - which is good? The next day the oil in the syringe had cleared up entirely. I don't know if that took minutes or hours.

The immediate question is whether this bubble entrainment is a also typical of other tractor hydraulic systems?? And would it clear up if the tractor ran longer?

rScotty

 

[Hersheyfarm]

well i guess i can clean all the grease off of my pumps and suction lines now. Ive checked mine after running hard for a while and its the same as it is when only running for a for a few.

 

[TBarD]

I am surprised by the amount of entrained air as well. This is not
foaming, it is entrained air (or other gas), i.e. small ~1mm bubbles of
air mixed in the oil. It looks excessive from the pictures, however I
do not know what is normal either. I will run another test myself when
I get a chance, but it probably won't be for a few weeks when I have the
tractor back to the garage.

Some amount of air entrainment in a warmed up system is probably normal.
Hydraulic oil at ambient temperature in an open system like we have will
contain 10-12% dissolved air by volume - this is when the oil is clear.
If we then heat the oil and pressurize it to 3K PSI in the lines then
depressurize when it returns to the reservoir, air bubbles can form as
the solubility of the oil is reduced. Air can also come out of solution
at the inlet due to decreased pressure in the suction, especially when
the system is cold, or if there is any clogging or other restrictions.

So a certain amount of entrained air in a warmed system is probably
normal. Excessive air entrainment likely indicates either an air leak
in the suction area, improper oil level at the air intake, or agitation
such as a splashing return which forcibly mixes air (this seems unlikely
in a properly designed system).

 

[Hersheyfarm]

I am running 1/4" above full right now to increase fluid volume in sump. I tried earlier to take a before and after sample from my mf4345 but my hose isn't long enough to reach the fluid in the sump, but I will. I expect it to be very violent in the sump of the m59 when it's running. Increased fluid volume may be needed.

 

[TBarD]

Another worrisome point here is running at 2700 rpm. None of the rest of us do that - when I am working it hard I run maybe 2200-2300 while wearing hearing protection (and it is hard to see that anything would be gained by running harder). You might run a test at these lower RPMs to see if the problem is unchanged. Any of the problems with flow restriction or fluid temperature, suction or agitation could be worse at max RPMs. If fluid temperatures exceed 140 or so I would be concerned, and it will tend to make air entrainment worse. Also fluid oxidation - your fluid when cool looks a bit colored, which would indicate oxidation due to excessive temperatures.

 

[dsgsr]

I fixed the problem with the Kubota oils. I use John Deere Low viscosity Hy guard, Been around for many yrs. and no problems. OH NO, JD blood in a Kubota it works just fine. OR you could go to Napa and buy 424 Hydro oil, Same thing Good quality.

David

 

[Hersheyfarm]

Another worrisome point here is running at 2700 rpm. None of the rest of us do that - when I am working it hard I run maybe 2200-2300 while wearing hearing protection (and it is hard to see that anything would be gained by running harder). You might run a test at these lower RPMs to see if the problem is unchanged. Any of the problems with flow restriction or fluid temperature, suction or agitation could be worse at max RPMs. If fluid temperatures exceed 140 or so I would be concerned, and it will tend to make air entrainment worse. Also fluid oxidation - your fluid when cool looks a bit colored, which would indicate oxidation due to excessive temperatures.

Kubota said to run at full rpm, mainly for heat dissipation, and running at full rpm's gives you their rated flow to work a couple of cylinders at a time with now slow down. Digging an 8' deep sewer at half rpm is crazy slow. Even your manual says the backhoe works best at tractors rated rpms. Kubota also assured me these machines are engineered to run full rpms all day long. Heres something else that will upset you, kubota is ok with 180+ degrees in the fluid temps. seems high but they should know.They advertise this machine as an industrial replacement for a full size TLB. This is straight from kubotas service tech, not the dealer.

The foamy fluid happens with just 5 min of warm up time, and is there after running hard. Ive checked it several times.

 

[Hersheyfarm]

I fixed the problem with the Kubota oils. I use John Deere Low viscosity Hy guard, Been around for many yrs. and no problems. OH NO, JD blood in a Kubota it works just fine. OR you could go to Napa and buy 424 Hydro oil, Same thing Good quality.

David

could you check your fluid for air after warm up for us? I could care less what brand I use just want the hydraulics to not fail again after warranty.

 

[rScotty]

Kubota said to run at full rpm, mainly for heat dissipation, and running at full rpm's gives you their rated flow to work a couple of cylinders at a time with now slow down. Digging an 8' deep sewer at half rpm is crazy slow. Even your manual says the backhoe works best at tractors rated rpms. Kubota also assured me these machines are engineered to run full rpms all day long. Heres something else that will upset you, kubota is ok with 180+ degrees in the fluid temps. seems high but they should know.They advertise this machine as an industrial replacement for a full size TLB. This is straight from kubotas service tech, not the dealer.

I share the same concerns about the high RPM that TbarD mentioned. I cannot tell from reading whether Kubota is saying that one should run at max RPM....or merely that one can. I agree that they do say in several places that the machine is capable of working at full RPM. Although they moderate that in the technical publication where the caution about exceeding an oil fluid temperature of 140F. So temperature rather than the RPM may be the limit.

Running at full speed in order to increase heat dissipation is an unusual argument to say the least! I'm betting that one didn't come from their technical staff. Frankly if someone told me that I'd sure take it with a large dose of salt.....better make that a 50lb block with trace minerals....

BTW, I didn't know that fact about hydraulic oil normally containing such a high percentage of dissolved air that TbarD mentioned. If so, then far less than ten percent of dissolved air by volume - coupled with an increase in temperature and varying pressure - is more than enough to create the entrained gas that we see in the samples. And if that is so, it is probably inevitable in any open hydraulic system (some JDs and some industrial equipment use a closed hydraulic system) That means that the entrainment we are seeing is not additional air from splashing, it would simply be an increase in bubble size due to the change in temperature and pressure. In fact, the entrainment would be made to look much worse by the simple act of using a syringe to take a sample....like I did...and that's something I think we all did.
Luck, rScotty

 

[rScotty]

......... Digging an 8' deep sewer at half rpm is crazy slow.

I'm glad you said that. The technical stuff is fun, but it boils down to your needing your backhoe to move faster. That makes sense. Have you timed the cycle times on yours? That might answer all the questions. And for warranty issues timing it would be definite and repeatable. Somebody suggested doing that a while back. Sorry, but I forgot who it was. Anyway it sounded good so I took a stopwatch along with my M59 Kubota manual and timed the various loader and BH cycle times on ours. It was sort of surprising how closely it matched the published specs.

Normally I run at about 2/3 rated speed and less than that for light work. At full rated RPM it feels less efficient because of the boom speed. Of course the problem might be with me rather than the BH, but in my hands it sure slams and throws things around.

Regardless of the RPM, The M59 controls don't seem to allow the BH bucket to move in all directions at once. If it could do all motions simultaneously that would certainly speed up the BH work. Some industrial machines have that ability and I miss it.
rScotty