Here I go again

[KentT]

Thank you, thank you, thank you!!!

BTW, I have my new pump installed and everything is running fine.

Glad to hear you've got it back in service, at least.

With no other info to go on, I'd recommend you have an oil analysis done, looking for contaminants and metal particles. Metal particles scratch and groove the swash plate in variable displacement pumps, and consequently they leak rather than build pressure....

Tolerances on the swash plate are tiny, and critical...

BTW, that pic is from this source which may help explain how they work:

Page 3

 

[SwampmanLA]

All the comments are interesting and I have pondered them all. What it boils down to is that something is unique to my tractor. The one thing that is really unique to this fine PT tractor is me and according to my wife prone to problems. So what have I been doing to cause the check valves on the tram pump to fail?

Reflection on this subject leads to this realization, I have been routinely stalling out the tram circuit trying to push into piles of dirt. This stalling would lead to the relief/check valve to erode as I have been moving lots of dirt! The result of an eroded valve would be loss of power and more treadle to compensate and more errosion............. Does this sound plausible?

 

[woodlandfarms]

My wife is electronically cursed. True. Anything that she has that is electronic breaks down in a short period of time.. Contant repairs are the norm.

For me, everything I own leaks oil. Runs like a top, leaks like a sieve.

I abuse my PT so I don't count all my constant repairs as PT issue, probably should...

 

[J_J]

All the comments are interesting and I have pondered them all. What it boils down to is that something is unique to my tractor. The one thing that is really unique to this fine PT tractor is me and according to my wife prone to problems. So what have I been doing to cause the check valves on the tram pump to fail?

Reflection on this subject leads to this realization, I have been routinely stalling out the tram circuit trying to push into piles of dirt. This stalling would lead to the relief/check valve to erode as I have been moving lots of dirt! The result of an eroded valve would be loss of power and more treadle to compensate and more errosion............. Does this sound plausible?

Who told you your check valves were eroding, or did you tear it down and confirm this? Hydraulic fluid usually doesn't cause erosion, but cavitation does. Erosion can also be caused by minute particle circulating in the fluid that are smaller than 10 microns, which is the filter you have. They have filters that go as low a 1 micron. Did PT give you any feedback on the pump you returned. Were both check valves eroded. You have I believe a check valve in fwd, and one in rev.

Again, a hydraulic gage would help determine the problem. If you know what the pressure should be or the operating pressure range, then you have a baseline. If what you say is true, and the check valves were opening, then you would be generating a lot of heat, because I believe the relieved fluid is routed back to the front of the pump. and and it also being a closed loop system, and you know that heat reduces viscosity

 

[BobRip]

Well thats interesting... a lot has changed, mine is dated 2004, the drawing anyway. Its a 2007 model , my lines for the hydraulic cooler go from the lift tilt valve through the cooler then back to a return port on the oil tank.
I have 5 pages of schematics labeled , 1) steering circuit,2)lift, tilt circuit, 3)pto circuit 4) wheel circuit 5)quick attach circuit .

I would have pt send you the correct diagrams

Kris

By all means get the correct diagram. When PT went away from the cable controlled speed control the diagram changed a lot.

 

[J_J]

Well thats interesting... a lot has changed, mine is dated 2004, the drawing anyway. Its a 2007 model , my lines for the hydraulic cooler go from the lift tilt valve through the cooler then back to a return port on the oil tank.
I have 5 pages of schematics labeled , 1) steering circuit,2)lift, tilt circuit, 3)pto circuit 4) wheel circuit 5)quick attach circuit .

I would have pt send you the correct diagrams

Kris

Hi Kris,

Would you scan post those hyd schematics as a file or pictures? I would like to take a look at them

 

[SwampmanLA]

Who told you your check valves were eroding, or did you tear it down and confirm this? Hydraulic fluid usually doesn't cause erosion, but cavitation does. Erosion can also be caused by minute particle circulating in the fluid that are smaller than 10 microns, which is the filter you have. They have filters that go as low a 1 micron. Did PT give you any feedback on the pump you returned. Were both check valves eroded. You have I believe a check valve in fwd, and one in rev.

Again, a hydraulic gage would help determine the problem. If you know what the pressure should be or the operating pressure range, then you have a baseline. If what you say is true, and the check valves were opening, then you would be generating a lot of heat, because I believe the relieved fluid is routed back to the front of the pump. and and it also being a closed loop system, and you know that heat reduces viscosity

Let me take these one at a time:
1. Terry told me the check valves are at fault, I assume that they have eroded in some way.
2. I did not tear down the pumps as they are in warranty.
3. I cannot comment on cavatation as I do not know what the symptoms would sound/feel like.
4. I'll have my oil analyzed for particles after the holidays.
5. I am considering rigging a 1 micron filter on the PTO circuit.
6. No feedback from PT on the first failed pump was offered.
7. I am following Terry's advice at this point and no suggestion about installing a gage has been offered.

Thanks for the comments and Happy New Year!

 

[SnowRidge]

All the comments are interesting and I have pondered them all. What it boils down to is that something is unique to my tractor. The one thing that is really unique to this fine PT tractor is me and according to my wife prone to problems. So what have I been doing to cause the check valves on the tram pump to fail?

Reflection on this subject leads to this realization, I have been routinely stalling out the tram circuit trying to push into piles of dirt. This stalling would lead to the relief/check valve to erode as I have been moving lots of dirt! The result of an eroded valve would be loss of power and more treadle to compensate and more errosion............. Does this sound plausible?

The stalling is not good practice. As you increase the load on the tram circuit, you should be easing up on the right treadle, not pushing down on it, if that is what you are doing. The tram pedal is a form of transmission control. It is a speed control only in the sense that a higher "gear" (down pedal) will give you a faster speed for any given engine RPM.

In the last few weeks, I moved about 18 tons of gravel with my PT-425 without stalling the tram circuit. I wiggle the bucket and work the treadle judiciously to get as full a bucket as possible, but sometimes I just have to settle for a partial load. It is easier on the machine. Whether or not the relief will erode from use, I can't say, but I am inclined to think it would have to be a lot more use than you have described.

Power-Trac gets their components from many sources and is always changing something, usually without mentioning it to their customers. The only safe way to know what is on any given machine is to verify it yourself. If someone posts that Power-Trac use a particular brand/model of component for any given purpose, don't take it as gospel. It may be true on the poster's machine, but it may not be true on yours. Part of the "fun" of working on PTs is tracking down what you really have and where you can get it for a reasonable price, or you can just use Power-Trac's in house part numbers and pay their prices.

According to Terry, Power Trac's parts diagrams and hydraulics schematics cover numerous models and model changes and may not exactly reflect what you have in your machine. In my experience, they also leave stuff out.

"We've never heard of that happening before," is possibly a well used recording with Terry's voice being synthesized by Power Trac's master computer (analog). It is probably triggered by a button in the sales office.

 

[Bob999]

5. I am considering rigging a 1 micron filter on the PTO circuit.

A word of caution. The selection of a filter involves trade-offs. A 1 micron filter will tend to load up and clog very quickly. It will also cause a larger pressure drop at a particular flow rate than a filter with a larger particle rating--such as 10 microns. The advantage of such a filter is that it will remove smaller particles from the fluid. Must farm/construction hydraulic systems don't use filters with a rating below 10 microns for inservice use. Rather 1 micron filters are more commonly used in off offline filter systems--such as a filter cart. Another approach, which JJ suggested, is to install a large 10 micron filter in parallel with a 1 micron filter. This achieves some of the advantages of a 1 micron filter but insures that there is relatively free flow of the fluid.

 

[SnowRidge]

5. I am considering rigging a 1 micron filter on the PTO circuit.

A series of articles that describes, among other things, the pros and cons of filtering at differing points in a hydraulic system can be found at Hydraulic Tutorials.

They are well worth reading before you start modifying the hydraulic system.