HST owners - Don't let this happen to you

[snoracer]

You cannot believe how careful/clean you have to be with axial piston pumps & motors. The slippers in both have to ride on a thin film of pressurized oil on the wear plate to keep from scrubbing. The cylinder barrel and port plate mating surfaces are the same. You loose that microscopic film of oil and start metal to metal contact, and it's just a matter of time before it's toast again.

When those units are assembled, they'll be run on a test stand going through the different pressures etc, the end of the test there will be an oil sample taken while its running and do a particle count, to see if anything is breaking down (scrubbing). If the sample is within acceptable specs, the unit is passed on to assembly. If its not, its rejected, tore down, faulty parts replaced and back to test.

Gear type units are more tolerable to debris then the axial piston type. You can get the high pressures with the axial piston pumps/motors that you cannot get with any other style. But the main culprit in them is foreign particles.

If he's already up and running I wish him well, and would advise changing out the hyd filter a couple times just in case. If any debris has found it's way to the pump it's already too late.

Thanks for the reply - I will post part 4, re-assembly, a little later, but for now I'll tell you that I was very careful about cleanliness during re-assembly.
dfkrug stressed that same point when I spoke with him during this repair. I wish I could have found a factory assembled complete unit, but they just aren't available. I did remove the pump from the backing plate and also took the pressure relief vales and springs out of the backing plate, in order to look for any foreign debris. Non was found. The pump was in perfect shape. As you suggested, I did replace every part in the motor. The cylinder barrel and wear plate came as an assembly. It was wrapped in a sealed plastic wrapper and completely coated in oil. I replaced the suction screen and hydraulic filter as well. The tractor is up and running fine. I'll put some hours on it and then change fluid and filter again.

 

[Toyboy]

Thanks for the reply - I will post part 4, re-assembly, a little later, but for now I'll tell you that I was very careful about cleanliness during re-assembly.
dfkrug stressed that same point when I spoke with him during this repair. I wish I could have found a factory assembled complete unit, but they just aren't available. I did remove the pump from the backing plate and also took the pressure relief vales and springs out of the backing plate, in order to look for any foreign debris. Non was found. The pump was in perfect shape. As you suggested, I did replace every part in the motor. The cylinder barrel and wear plate came as an assembly. It was wrapped in a sealed plastic wrapper and completely coated in oil. I replaced the suction screen and hydraulic filter as well. The tractor is up and running fine. I'll put some hours on it and then change fluid and filter again.

It would not take hours to circulate oil through the system. I think I'd do it sooner rather then later just to be safe.

 

[snoracer]

It would not take hours to circulate oil through the system. I think I'd do it sooner rather then later just to be safe.

Filter only, or filter and fluid ?

 

[Toyboy]

Filter only, or filter and fluid ?

I'd start with filter & strainer. If you've run it for awhile, hopefully any particles would be picked up by both. If you see signs of debris on strainer, change out fluid also. It don't take much to compromise the bronze when your mating part is hardened steel.
The normal procedure when you have a failure like this (normally it's running), is to flush the system and change filters. Filters are cheap compared to what you just went through.
If this works out OK for you in the long run.... Go Buy a Lottery Ticket!

 

[snoracer]

Part 4 - re-assembly

Took almost a week for all the parts to arrive. The first thing I did was assemble the hydro motor. I followed the JD tech manual directions to the letter.
As stated earlier, I made absolutely sure that everything was spotlessly clean. Tools, work surface, parts, everything. dfkrug mentioned during one of our conversations, that you even have to be careful about what rags are used. DO NOT USE PAPER TOWELS, they give off too much lint and paper dust. Then I removed the hydro pump from the backing plate in order to see if there was any damage or debris. It looked perfect. There was no sign of metal shavings or debris of any kind. The port valve plate, which has a bronze plated surface, was in great shape. I did the fingernail scratch test on it to feel for small scratches, non were found. Next, I disassembled the backing plate, per the tech manual directions. It's important to make sure all parts are put back in their original and correct locations. The relief valves springs look very similar, but they have different spring rates, so mark them as you disassemble them. As the fluid drained from the backing plate, I watched closely for any debris. There was none !! With all that done, I was then able to remount the pump and motor to the backing plate.


reassembled hydro unit ready to go back in

Once that was mounted, I began the long process of putting the tractor back together again. Thank god for smart phones. I took a ton of photo's as I
tore this thing apart, cause I knew I wouldn't remember were everything went. I have a good memory, it's just short !! So, between the tech manual and my photo's, I was able to get her back together successfully. While I was at it, I also installed a block heater. I bought it from JD, specifically for this engine. It has already come in handy, since the temps have been below zero a lot lately. She starts like it's summertime. I also use AMSOIL 15w40 synthetic oil in the engine. I have put about 10 hours on it, and all is well, so far. I will change the hydro filter now and check for debris, as per suggestions from earlier posts here on TBN.

Altogether this experience cost me a little over $2000.00, and I was without the use of my tractor for about 3 months. The moral of this story is: DON'T TRAILER YOUR TRACTOR WITHOUT TYING IT DOWN !!!

Again, Thanks to all you TBNers who have posted such helpful info. This is a very knowledgeable bunch here. Once again a very special thanks to dfkrug for all his help and encouragement. Thanks Dave!!


Puttin her to good use !!!

 

[k0ua]

Well, I would not have thought it would have busted the hydro motor like that, but all things considered you got off pretty easy considering what could have happened. You learned a valuable lesson, and guts enough to share it here so others could learn from it a lesser cost. Nice write up and Good on you..

 

[George2615]

Ditto what James said.
Excellent job making the repairs and posting.

 

[Code54]

Great work and thanks for sharing it with us - learned a few things!

 

[Toyboy]

My last suggestion on this is, when you change the hyd filter, open it up and see what you filtered out.

 

[crazyal]

Glad it worked out and nobody was hurt (other than your wallet). It's easy to cut a corner or two and when it works out it becomes the new way of doing things. Now you have a lot more confidence in any future repairs that may be needed.