Broke Hydrostat twice? Why?

[Bob Christensen]

Hi Folks,

Haven't been on here for years now, but about 8 years ago you were super helpful in getting a tractor when I knew nothing and then keeping me alive while I learned.
I wound up with a TYM 273-27 HP CUT with all the attachments. Now 8 years and 1300 hrs old I love it.
My issue here now is that at about 400 hours the Hydrostat broke - tractor wouldn't move at all. It was replaced under full warranty and was fine again.
A few weeks ago, almost all forward motion stopped. Reverse was fine. Implements were fine.
I reversed the relief valves and still no forward.
Checked pressures:
Rear (backhoe) 1800 lbs - this is correct.
2 check valves at Hydrostat - 500 lbs each - should be 2500 lbs.
Feed pump check point - 125 lbs - correct.
I have no nearby dealer so I hauled it to Jordan in Post Falls, Idaho. Can't say enough good about these guys.
They diagnosed faulty Hydrostat. Had a low hrs. used one on the shelf! Replaced and all is again well.
My question is that since everyone says there is rarely a problem with these Hydrostats, how did I break 2 of them? and how do I keep from breaking another?
Background:
10 acres of mostly old growth forest. Path building. Lots of bucket and grapple work.
Hard work - 1300 hrs now but oil and filters always changed with the best - Mobil 1 and Kubota Super UDT transmission fluid.

I am putting this in Owning/Operating instead of the TYM section because of the lack of traffic there and I think this could have happened to any tractor.
I have always received lots of help from this site and I thank you in advance for any advice you can give me now.

Bob

 

[HEC]

To bad Jordon couldn't give you a heads up with what is going on . It is beyond me for sure , but others may jump in and offer some help .

Good Luck

 

[Raincoast]

It would be great if you could get a teardown report when the unit goes in for repair or overhaul. It would be worth asking the dealer if they could send you a copy... That is, IF the unit is going to be repaired. They might just toss it in the scrap bin.
Good luck. I hope third time is the charm for you!

 

[Billrog]

Jordan can't say this is a problem but are you running at to low of an rpm ? If this is the case you could be starving the pump of oil which could lead to damage. This is often the case with the hydraulic drive motors on skid steers when run at low rpm.

 

[Bob Christensen]

Jordan can't say this is a problem but are you running at to low of an rpm ? If this is the case you could be starving the pump of oil which could lead to damage. This is often the case with the hydraulic drive motors on skid steers when run at low rpm.

I have often wondered what the proper RPM is.

I almost always run at about 1800 RPM. Red line is 2700.

This time of year Jordan is pretty busy. They say that since they're curious too they may rip into it this winter, and if so they will tell me what they find.

 

[Bob Christensen]

The above is not to mean that I really expect Jordan to solve the problem any time soon or even at all.
I'm relying on someone here to hopefully recognize the problem and tell me if I' doing anything wrong.

Thanks, Bob

 

[SweBota]

Is your hydraulic oil cooler working correctly? Put an oil temp meter in the return path somewhere and monitor the temp. I have had a hydro pump failure after 400 hrs in a smaller machine due to high temps.

/Marcus

 

[Billrog]

I think running at 1800 is fine my case 20hp has 3700 hrs. and I ran it any where from 1200 to 2000 most of the time plowing snow and higher when splitting wood, tilling or running a flail. It still works just fine and never a trans. prob.

 

[Bob Christensen]

Marcus, Hmmmm...
I do a lot of compost turning. My engine has never overheated according to the dashboard gauge, so I haven't been concerned about heat.
I blow the radiators out from time to time when they seem encrusted with compost or dirt but now it occurs to me that the tranny cooler is small and sits in front of the main radiator and gets covered first.

So there may be a time when it is clogged but the engine radiator is only partially blocked and in my cool climate this does not show up on my engine temp guage.

I'll never know now,of course, because thanks to you this will never happen again.

Anyone want to chime in on whether this was likely the culprit? I might add that since the other main task for the poor beast is clearing and maintaining paths in a forest, random sticks have long since destroyed the front grill, making easy access for mulch dust, etc.

Plus turning over a,say, thirty ton pile of manure would perhaps make the tranny want to heat up without perfect cooling?

 

[Grandad4]

I'd pay attention to what Marcus has noted. There have been a few times when I have worked the tractor hard enough that the hydraulic fluid got pretty hot. On mine it took intense heavy FEL work on a 95 deg. day to get to that point. Began to smell a whiff of hot fluid - it has a unique aroma - and touching one of the FEL lines confirmed it was too hot to touch. Backed off the pace of work and it cooled down to more normal temperatures, no harm done and I learned to watch for overheating the hydraulic fluid in extreme conditions. While it's normal for the fluid to get good and hot as the tractor works - 180-220 deg is probably typical, when it gets well beyond that there's the potential for harm. Every situation is different of course but heat seems like a real possibility in setting up the conditions for your HST breakdowns.