Broke Hydrostat twice? Why?

[Bob Christensen]

Fluid ... You're an idiot.

Bob ...I'm sorry, but I don't think that excessive heat due to fluid quality had anything to do with your failures. Many many people use store brand fluid without failures. And, like Coyote mentioned, HST's are not prone to failing.

No, I don't think the oil 'caused' the problem.

But there seem to be a half dozen things, perhaps the worst being the detent thing and sometimes crudded up oil cooler that maybe caused the problem, and if so, starting with thinner oil could have contributed to the problem.

Or from the other side if we're seeing damage caused by 5 years of elevated temperature, perhaps thicker, synthetic oil might have extended the life.

But no ,this is surely not the meat of the issue.

 

[murphy1244]

Tim you are right,Fluid is a Idiot. Good luck Bob.

 

[oldnslo]

HST operation:
ALL HST's require some form of of make up flow to compensate for leakage loss. This is done with designated charge pumps on most models but some like the Kubota BX series use oil from the implement/ steering pump for this function. This flow is typically around 20% of the HST pumps displacement.

If the RPM's of the engine are to low the charge pump system may not have enough flow to compensate for the leakage losses. As the oil / HST temperature rises the leakage increases and depending on the condition of the charge pump the charge flow may decrease. This is part of the reason for running at higher RPM's.

Typically if there is not enough charge flow the HST will be noisy. If you are right on the edge of loosing charge pressure from insufficient charge flow this could cause some cavitation. Cavitation is death to all pumps and motors.

I frequently use high range on my HST for doing loader work but I also do not allow the HST to "stall" for an extended period of time. "Stalling" an HST will send the fluid over the cross port relief and right back into the pump inlet and over heat the pump in a very short time.

definition of stalling: Point at which the tractor tires are not spinning and the HST is going over relief. You may or may not hear the relief valve function over the diesel engine.

From what you have described I would be surprised if over heating was the only issue since it worked in one direction and not the other.

Hope you can find the root cause since odd things do happen in mechanical equipment.

 

[Bob Christensen]

HST operation:
ALL HST's require some form of of make up flow to compensate for leakage loss. This is done with designated charge pumps on most models but some like the Kubota BX series use oil from the implement/ steering pump for this function. This flow is typically around 20% of the HST pumps displacement.

If the RPM's of the engine are to low the charge pump system may not have enough flow to compensate for the leakage losses. As the oil / HST temperature rises the leakage increases and depending on the condition of the charge pump the charge flow may decrease. This is part of the reason for running at higher RPM's.

Typically if there is not enough charge flow the HST will be noisy. If you are right on the edge of loosing charge pressure from insufficient charge flow this could cause some cavitation. Cavitation is death to all pumps and motors.

I frequently use high range on my HST for doing loader work but I also do not allow the HST to "stall" for an extended period of time. "Stalling" an HST will send the fluid over the cross port relief and right back into the pump inlet and over heat the pump in a very short time.

definition of stalling: Point at which the tractor tires are not spinning and the HST is going over relief. You may or may not hear the relief valve function over the diesel engine.

From what you have described I would be surprised if over heating was the only issue since it worked in one direction and not the other.

Hope you can find the root cause since odd things do happen in mechanical equipment.

Thanks for that really goodexplanation, oldnslo. It makes it much easier to visualize what's going on in that hydrostat.

 

[Coyote machine]

I agree with TSO and Murph, what's his name is clearly an idiot.

Now back to business. TYM's aren't noted for HST failures, IIRC what Bob said earlier in this thread. BUT two failures on one machine is a possible indicator of an operator that may have unknowingly killed them through ignorance of what conditions of use were doing to their life expectancy. I'm NOT saying Bob is ignorant; rather I'm saying, ignorance/lack of needed knowledge of cause and effect, for which he is no longer ignorant of how to prevent future mishaps, might have led to the unfortunate outcomes leading him/us to where we are in the learning curve.

 

[MHarryE]

This thread has been interesting but also has lost civility. People bad mouthing each other over Bob's broken hydro - how about donations to Bob so he can drop everything and tear the hydro apart taking pictures of everything he finds, including the locking pin that somebody failed to install properly.

Cavitation - a silent killer - but wait, not so silent. With my L3710 my dealer gave me a paper printed by Kubota showing why Super UDT (in those days) helps cut down hydro noise in colder weather. It didn't give an in depth technical description but instead printed out flow rates at given temperatures showing how much improved Super UDT was at cold temps. Users on here have confirmed that by found. Actually the increased noise level using UDT is due to the suction filter restricting cold oil flow to the hydraulic pump which in turn feeds the charge pump. The charge pump in turn provides oil to the hydro high pressure and control circuits. John Deere supplies their low viscosity oil for the same reason in their hydros. Of course there are even better oils out there but selecting them is the challenge. Companies publish their viscosities at 100 and 40 (Celsius) but what is the viscosity at -20 Celsius when you start? What is the viscosity when the oil reaches 120 when brush hogging and the cooler plugs? Makes you want a gear transmission hut I haven't shown you my failed gearbox pictures yet.

 

[Coyote machine]

I'll speak for just myself. I don't take kindly to someone coming into a thread and throwing some asinine attitude around; especially when it's clear they haven't read the thread, and they tell the OP to buy their brand tractor 'cause it will live forever, blah, blah, blah. I don't like to jump on the calling the poster an idiot, but I do want them to know their useless waste of time comments are not wanted. If they want to contribute something positive then do so, but otherwise don't go to the your tractor is junk, mine is golden, BS place.

And, as I said above back to business.....

 

[Bob Christensen]

This thread has been interesting but also has lost civility. People bad mouthing each other over Bob's broken hydro - how about donations to Bob so he can drop everything and tear the hydro apart taking pictures of everything he finds, including the locking pin that somebody failed to install properly.

Cavitation - a silent killer - but wait, not so silent. With my L3710 my dealer gave me a paper printed by Kubota showing why Super UDT (in those days) helps cut down hydro noise in colder weather. It didn't give an in depth technical description but instead printed out flow rates at given temperatures showing how much improved Super UDT was at cold temps. Users on here have confirmed that by found. Actually the increased noise level using UDT is due to the suction filter restricting cold oil flow to the hydraulic pump which in turn feeds the charge pump. The charge pump in turn provides oil to the hydro high pressure and control circuits. John Deere supplies their low viscosity oil for the same reason in their hydros. Of course there are even better oils out there but selecting them is the challenge. Companies publish their viscosities at 100 and 40 (Celsius) but what is the viscosity at -20 Celsius when you start? What is the viscosity when the oil reaches 120 when brush hogging and the cooler plugs? Makes you want a gear transmission hut I haven't shown you my failed gearbox pictures yet.

MHE, I appreciate your concern, but I don't think the thread has lost civility. Ten pages , a hundred comments almost all helpful and kind. No, this problem touches on several issues on which people hold fervent beliefs, and only one person forgets himself. That might be a record

Anyway, no donations needed. I have received the HST back from Jordan and dafter tomorrow we're heading down to Cali to take advantage of Dkrug's offer to take it apart. And we are bringing a camera!

All this running around may look goofy to some, but there are reasons.

The trip to Idaho put me together with a dealer known to this board to be one of the good ones and I can confirm that whole heartedly. I also knew they had a lo Hours HST sitting on the shelf.

Plus, after they fixed it I was able to go visit my older sister who lives in northern Idaho bringing a tractor, box blade and FEL plus a pickup full of horse manure compost - I'm really getting good at making that stuff. Spent two days working around her place. Got more satisfaction out of that...

The trip to California will be 1,000 miles each way on the Coast Highway. I really love to drive and we'll be taking our new to us car that is a joy to drive.

Oils.
I think you meant to say 220 degrees which is close to 100 centigrade. And as for -20, well pour point would perhaps be more interesting than vis.

I can't even find Super UDT around here anymore. When I went to buy some recently I got Super UDT2
Which Kubota makes sound like full syn, but is actually a blend. At unknown proportions.

Gotta go. The firewood guy just drove up. I'm wholesaling about 10 cords of logs to him and I have to pull the last of it out of the woods with my tractor that I love.

 

[SweBota]

I think you meant to say 220 degrees which is close to 100 centigrade.

I think he meant 120 Celsius which is the point where most oil temp meters start showing red. Some don't until 140, and some start at 100, but in any case it's now my believe that HSTs prefer oil considerably cooler and on the machine where we added a lacking oil cooler (and a temp gauge) we now rarely see temps over 75, which feels good. I don't think HSTs should be compared to engine oils when it comes to acceptable temperature, but I have no hard data confirming this. All my temps are in Celsius, of course.

BTW, please don't use "centigrade" for Celsius, that use was officially abandoned in 1948 due to disambiguity. A centigrade is actually a measure of angle, 1/100th of a gradian (or gon). As the gradian is 1/400th of a turn, a centigrade is 1/40000th of a turn. Related to the milliradian which is 1/1000 of a radian, another angle measure which approximates to the "mil" for those who have worked with rangefinding in artillery....


/Marcus

 

[Jkott]

No one should actually be paying $200 for a 5 gallon Paul of Amsoil synthetic. Throw a $10 preferred customer membership in your cart and it's only $139. It was cheaper than the F200 I prices at my New Holland dealer earlier this year.