M59 hydraulics got slow and weak.

[Hersheyfarm]

I finally got a chance to check the hydraulic fluid temperature, after working the backhoe for a few hours peeling a bank back. I have an excavation with a cut 6-7 feet high, vertical, at the back where it cuts into the hill (nothing is flat around here). The job was to slope it back 12' or so above the 4' level. Anyway, a lot of typical backhoe work, a lot of cylinder action and fluid motion. The ambient temperature was about 65. After 90 min or so at a moderate level (2K RPM) I measured 140 at multiple spots with the IR gun. The temp down the fill hole was not appreciably different than the reservoir housing or the pump end of the main hydraulic pump. I increased the RPMs to 2.2K and ran hard for another couple of hours, after which the temps averaged about 158 measured a multiple locations. This is higher than I am used to but I was working it harder at a higher RPM than usual (I did not want to go any harder as I was on the edge of a 7' vertical cut and anyway this was precision work trying to get a level surface). I could not test the in/out temps of the oil cooler as they are not easy to get to while the engine covers are on. My feeling is that these are normal temps when working hard for hours - they are not much different than my truck AT when driving unloaded. At no point was there any issue with performance or power.

Just think if ambient temps where 85 degrees you most likely would see 178 temps. Run at 2700 rpm(the way kubota wants us to) digging 10' deep holes in wet sticky clay. yup, there goes pumps. I think kubota dropped the ball with the m59 and their answer is 180+ temps are ok.

First, I dont think they put a big enough cooler on it, second the engine mounted pump for this kind of flow is a mistake. Theyve designed a 45-50k hobby machine instead of a "full size TLB replacement" like they claim. I'll try and keep it because it is a usefull chore tool around the farm, but I am going to have to back to full size tlb.

 

[rScotty]

Whoa! I'm starting to wonder if I got the oddball M59!!? Mine works remarkably well, and has so much BH power at low RPM that everyone - including my buddys with their full size TBLs - find ourselves grinning at just what this M59 BH will do. Not that it will replace a full size TBL, nobody's running scared from that.... but that wasn't the expectation.

We keep running into these differences with the M59 BH manuals. (see posts 161-164) It sounds like there might have been several versions.
You say:
"Run at 2700 rpm(the way kubota wants us to)"
The manual that came with my 2008 M59 simply doesn't say anything like that that. If anything, it advises 75% of 2700 = 2025 rpm (on page 7) as best for the BH for "special digging conditions, optimal fuel economy, and reduced noise".

Where you note,
"I think kubota dropped the ball with the m59 and their answer is 180+ temps are ok."
Here, my Kubota info is way different. There are lots of references in the official workshop manual specifying the operating range of the hydraulic system is from 104 to 140F. Nothing higher is mentioned in there. Certainly not 180F. From my own engineering background I don't know about the ability of the oil to handle more temp, but I do know about high temp O-rings and lip seals. And 180F implies a whole different material world than 140F.

"........ambient temps .....85 degrees"
Neither manual talks much about ambient temp versus coolant temps. Not that I blame them for that. It's important info but rarely seen. Cooling problems are complex little worlds...not easy at all....but raising the ambient air by some degrees probably won't do the same to the hydraulic system temps. That is, it would probably raise the oil temp less than that, but a system right on the edge could go the other way too. It's just not straightforward.

I'd say you have a point if you want to pursue it. Near as I can tell from both your and TbarD's measurements, more cooling coupled with a thermostat sounds like it would be an advantage. More on this below...

"I don't think they put a big enough cooler on it, (and) the engine mounted pump for this kind of flow is a mistake."
Interesting thought. I haven't looked at the pump mounting; wouldn't that be hard to change? But either way, you may be onto something with the additional cooling idea. Anything can be improved. There is a whole industry for aftermarket tranny and engine cooling on pickup truck trannys. Particularly for trucks that are working hard. Ford, GM, and Dodge left a lot of this to the aftermarket folks. Wonder why? But thanks to them for doing so and no reason we can't do the same on a tractor.

"a "full size TLB replacement" like they claim."
Sounds like this tractor is a disappointment to you. I wish you had a more responsive dealer or that Kubota would step up with some real tech info to help out. As much as the M59 has been useful on our land, I wouldn't expect it to replace a full size TBL like a Case 580. (my second choice). Apparently someone claimed that it would do that for you, but in fairness to Kubota if they publish such a claim I haven't seen it.

As a side note, for my own uses I wonder why using the BH at lower engine speeds isn't mentioned in the manual? How could lower engine speeds possibly be a detriment? The BH manual doesn't say a word about operating at less than 75% rated RPM. Anyone got any ideas? Maybe it doesn't get hot enough?? My own special digging conditions in rock rather than dirt are such that I often run at more like 50% of rated rpm instead of 75%. It moves a little slower; that's what's needed when working rocks. The force is also a little less, but since the silly thing seems to have too much force for it's own good anyway that just keeps me from breaking things.
Luck, rScotty

 

[Hersheyfarm]

this is my page 7.
it clearly suggests not running less than 75% of rated rpm.

The 180 degree thing is not printed. It comes from what the dealer said the tech hotline told them(kubota) after my concern, and the kubota service reginal rep. plus if you search the kubota forums here i beleive I have read other posts where members where told the same.

as far as my machine here it is probably the only '08' with the updated pumps, and all the adjustable check valves on the backhoe have been guaged and set for maximum pressure. But my main concern is: with common sense, and with all the hydraulic 'experts' here that I agree with, my machine got too hot and burnt the pumps up..working within the parameters kubota gives.

 

[TBarD]

The main hydraulic pump is not mounted on the engine block, it is separated by several inches of air, and is mounted on a gear housing which eventually does get back to the engine (it has to of course since the pump is direct drive by mechanical gearing). Some heat will certainly flow from the engine to the pump through the gear housing, however 15 GPM or so of oil are continuously flowing through the pump. Back when I took my temperature measurements the pump at dead center was the same temperature as the oil (rising at points toward the engine of course). Some heat will also flow from the engine through the clutch and HST drive. We do not know how significant this source of heat is compared to the heat generated by the hydraulic system itself, but I doubt if it is a major factor since the engine temperature is a constant once operating temperature is reached, while the temperature of the hydraulic system fluctuates with the work load.

The M59 is by design not all that big and massive, but nonetheless has a lot of power. It is not surprising that the temperature of the hydraulic system will rise when the tractor is worked hard for long enough, and all that steel and the 12 gallons of hydraulic oil gradually heat. I had to run it harder than needed to get the job done to get it up to 158deg, and that took several hours. The oil cooler has a limited capacity and can only remove a certain amount of heat (increasing
cooling is likely impractical). For most purposes I will continue to run mine at 2 - 2.2K and reserve higher RPMs for shorter periods of time when max power is needed. If the machine is going to be worked hard for long periods of time I think it wise to monitor the temperature and back it off a bit if it gets too high.

 

[Hersheyfarm]

The manual that came with my 2008 M59 simply doesn't say anything like that that. If anything, it advises 75% of 2700 = 2025 rpm (on page 7) as best for the BH for "special digging conditions, optimal fuel economy, and reduced noise".

on page 85 of your tractor manual is there a glued in page where they changed something with the filters?

 

[rScotty]

on page 85 of your tractor manual is there a glued in page where they changed something with the filters?

Lets see...that would be the operator's manual....No. There don't seem to be any glued-in page anywhere in there. You mean I'm missing something?! Uh-Oh....
Here is my page 85. Sort of poor copy, but hope it's legible.
rScotty

 

[Hersheyfarm]

View attachment 280916View attachment 280917

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

Now that my warranty is out this is really troubling me. I am also thing about upgrading the cooling system because heat is what slows my hydraulics down.

 

[rScotty]

Now that my warranty is out this is really troubling me. I am also thing about upgrading the cooling system because heat is what slows my hydraulics down.

So yours is still having problems when you work it hard enough to get hot? From the literature it should be able to handle the heat. But adding more cooling has got to be a good thing. What are you going to do?

I think we concluded that I work our M59 more lightly than you do yours. And that may be why I don't see any problems. But if you have excessive hydraulic heat then that is a problem no matter what the cause. And I agree that it needs fixing, and expect that the "fix" will be to add some sort of additional cooling.

The odd hydraulic things that I do see or hear - like the entrained gases we photographed and the whine when starting cold - are clearly things that Kubota didn't quite get right. So far I can't say that either one has caused a problem for us.... So to be fair I can also say that even if Kubota didn't get it clear right, they didn't get it wrong either. And so with some finger-crossing they might even be considered normal.

For that matter, the amount of entrained air that the attached photos showed might be normal for tractor hydraulics throughout that industry. Although putting on my fluids engineer hat allows me to say with authority that the cold whine and the gaseous entrainment are probably related. And also IF that amount of gaseous entrainment is considered normal.... then the whole industry needs to do some work. It is easy work, but it does need to be done for reliability reasons.

Our M59 didn't used to whine about the cold.

Of course when I was younger I didn't whine so much about the cold either....
Enjoy! rScotty

 

[mike69440]

As a 2005 L39 owner and the owner of a 1997 Komatsu PC75UU-2E 18,000 lb Excavator, I've been a troll following this thread. I'm a bit concerned about damaging the pumps on either of my machine as I am not in a position to afford to repair them if they fail, so I want to pick up any tips on operation or maintenance.

I tend to run both machines around 75%, maybe a bit more on the excavator and a bit less on the L39.

The real heavy digging I now do with the excavator mostly, but prior to the excavator I wore out a few sets of teeth with the L39 BH. I’ve move stupid amounts of material with the loader. The L39 has 1,700 hours and I have done 1 hydraulic oil change at about 500 hours and filter changes at 500 hours and 1000 hours. RP hydraulic fluid mixed with various other synthetics to make up loss for blown hoes etc. is the hydraulic fluid in the L39 and I use Komatsu Green powertrain oil in the excavator. UDT seems to be a bit noisier, but I have no other onion good or bad for the stuff.

The L39 main reliefs are set to max or maybe 5% above, nothing crazy. Same goes most of the circuits of the excavator. I suspect I've gotten the L39 hydraulic up to about 150F, but this is working the machine very hard.
I've never experienced a loss of hydraulic performance due to temp. same goes for the excavator, The excavator worked hard will put the engine temp in the red on a hot day and the oil hydraulic oil temp goes over 180 F. I back off for fear of damaging the engine or hydraulics, but it still wants to work just as hard with hot oil as warm oil. Hot oil does not cause hydraulic pump noise or slow operation.

So I'm wondering if something in the basic design hydraulic system of an M59 is allowing the oil to foam or cause other problems.
Although rated HP of the excavator is the same as an M59, the hydraulic reservoir hold 30 gallons of oil and the pumps put out almost 50% more volume and pressure than the M59, while not suffering The issues some M59 owners seem to have.

 

[dsgsr]

I have not experienced any Hydro whine in cold weather. I've been working the M59 in below 0 temps, I have John Deere Low visc hyguard for hydro oil. Since I changed to JD hyguard I've not had any problems in Cold or hot weather. I have yet to find a large enough Hypo syringe with hose to take a pic. of the oil for you folks.


David