Hydra-Mac drive motor wont pump

[Mxlord]

I have a problem with a old hydra mac skid steer. Awhile back a press pin broke on one of the drive motors, I replaced the pin and now I can't get it to pump oil. I've tried every thing I can think of. It was working great before the pin broke.

 

[SkidRoe]

What model of Hydra-Mac skid steer do you have?

 

[Mxlord]

What model of Hydra-Mac skid steer do you have?

I'm not positive but the tag say's either 620 or 820. Tag is just about worn out.

 

[Mxlord]

I'm not positive but the tag say's either 620 or 820. Tag is just about worn out.

I just put a pic of it on my profile.

 

[SkidRoe]

I just put a pic of it on my profile.

Looks a lot like an 8A, which is the same as a Gehl 2500. I can move your post to the Gehl Forum, if you like.

 

[Mxlord]

Looks a lot like an 8A, which is the same as a Gehl 2500. I can move your post to the Gehl Forum, if you like.

Yes please. I need all the help i can get.

 

[SkidRoe]

Yes please. I need all the help i can get.

Okay, moved. Cheers - SR

 

[vinito]

Which pin are you talking about? there are pins connecting the control lever to the swash plate shaft and a pin for the drive shaft. Also if you had to crack it open there are a couple more places that use pins, but I'll assume you didn't have to do that yet.
The first thing that comes to mind is that the pin might have broken for a reason in the first place and the original fault is still a problem. Hopefully there isn't a buch of shrapnel inside the hydrostat which doesn't take long to trash it, but that is a possibility so you might prepare yourself. Did you re-check your repair to see if it didn't just break again? This might further indicate another problem which again isn't fixed yet.
At any rate, if you could be a little more specific, we can probably help you troubleshoot it.

 

[vinito]

Which pin are you talking about? there are pins connecting the control lever to the swash plate shaft and a pin for the drive shaft. Also if you had to crack it open there are a couple more places that use pins, but I'll assume you didn't have to do that yet.
The first thing that comes to mind is that the pin might have broken for a reason in the first place and the original fault is still a problem. Hopefully there isn't a buch of shrapnel inside the hydrostat which doesn't take long to trash it, but that is a possibility so you might prepare yourself. Did you re-check your repair to see if it didn't just break again? This might further indicate another problem which again isn't fixed yet.
At any rate, if you could be a little more specific, we can probably help you troubleshoot it.

Sorry, I wish we could edit posts so we could keep things more tidy.
I realized that along with more specific info on which pin you replaced, it would also be very useful to know stuff about what it was doing before and what it is doing now. Don't be worried you're being boring by making it too long, the more information the better, just try to be clear and accurate.
So is it "howling" now? Grinding or knocking? any noises you hear can help us figure it out. Does the left or right hydrostat work and the other doesn't now or does it not want to move at all? Does it budge at all, just for a moment at first, weakly but steady or just totally "dead"? Any info on what you see, hear, did or didn't do will be helpful.

 

[Mxlord]

Sorry, I wish we could edit posts so we could keep things more tidy.
I realized that along with more specific info on which pin you replaced, it would also be very useful to know stuff about what it was doing before and what it is doing now. Don't be worried you're being boring by making it too long, the more information the better, just try to be clear and accurate.
So is it "howling" now? Grinding or knocking? any noises you hear can help us figure it out. Does the left or right hydrostat work and the other doesn't now or does it not want to move at all? Does it budge at all, just for a moment at first, weakly but steady or just totally "dead"? Any info on what you see, hear, did or didn't do will be helpful.

The pin that broke is the one on the outside that hooks the gear to the pump shaft. The pin has broke before because the holes on the gear and on the shaft were really worn out, so I decided it was a good time to weld the holes and redrill for a good fit. While I had the motor apart I checked the other pins and they were all good. I'm not hearing any noises. Now there are two brass plates inside, are they the same?

 

[vinito]

The pin that broke is the one on the outside that hooks the gear to the pump shaft. The pin has broke before because the holes on the gear and on the shaft were really worn out, so I decided it was a good time to weld the holes and redrill for a good fit. While I had the motor apart I checked the other pins and they were all good. I'm not hearing any noises. Now there are two brass plates inside, are they the same?

If I'm understanding you correctly, the pin you replaced is the one connecting the belt pulley to the pump shaft by way of a spline. On the outside of the hydrostat, that's the only "gear-looking" thing I can think of. As long as the pin hasn't sheared off, that shouldn't be your problem.
The only other possibility I can think of is the charge pump gears, which are kind of outside the hydrostat but still inside it too. It's basically the entry point of the hydraulic oil into the hydrostat, but it's still internal to it. If that is the pin that went south, then something might be off I suppose and be causing the issue because the charge pump must be working properly since it feeds fluid downstream to the drive pump cylinders. Also, one thing that comes to mind if you have taken the charge pump cover off is that it must be correctly oriented when you reinstall it. It can be flipped 180º otherwise it will not operate properly, so you might double-check that. But if you've welded on the charge pump gear, that would be a tricky thing to get right. That's a pretty critical and complex part to be messing with at all, and as a machinist I doubt there's anything on those even I would try repairing. The shaft isn't a big deal. But the gear engages the pin via a slot rather than a hole anyway so I doubt that's what you were referring to.
Have you checked this writeup? Sundstrand rebuild It is pretty good and informative. You might get some good ideas there. It varies a bit from what we have in our loaders, but it's still all basically the same.
Regarding the brass plates inside, no they are not the same. One is for the pump and the other for the motor and they must be installed correctly or they won't work. You just need to look for the little notches in the valve slots. The motor has them in all four corners but the pump only has them in two corners. I don't know what it will do if reversed, but it won't operate properly. From the write-up linked above:

So armed with this info, you might re-check your work and make sure it went together correctly on your first try. If one or two of those parts was installed wrong, the drive won't work correctly for sure, and maybe not at all. I would start with the charge pump cover and make sure it's not flipped 180º. Off the top of my head, that seems most likely. Check the link above to see the proper things to look for. If it's not that, I suppose it could be you've transposed those two bronze-faced valve plates inside.
Not sure if this will be helpful yet, but here's my post about a hydrostat rebuild. It's not very informative yet (I'm still in the middle of it), but maybe there's a useful tidbit there anyway.
http://www.skidsteerforum.com/DesktopDefault.aspx?tabid=54&frmView=ShowPost&PostID=92178
At any rate, I'm guessing your repair work is probably OK and the problem is likely to simply be a reassembly error.

 

[vinito]

If I'm understanding you correctly, the pin you replaced is the one connecting the belt pulley to the pump shaft by way of a spline. On the outside of the hydrostat, that's the only "gear-looking" thing I can think of. As long as the pin hasn't sheared off, that shouldn't be your problem.
The only other possibility I can think of is the charge pump gears, which are kind of outside the hydrostat but still inside it too. It's basically the entry point of the hydraulic oil into the hydrostat, but it's still internal to it. If that is the pin that went south, then something might be off I suppose and be causing the issue because the charge pump must be working properly since it feeds fluid downstream to the drive pump cylinders. Also, one thing that comes to mind if you have taken the charge pump cover off is that it must be correctly oriented when you reinstall it. It can be flipped 180º otherwise it will not operate properly, so you might double-check that. But if you've welded on the charge pump gear, that would be a tricky thing to get right. That's a pretty critical and complex part to be messing with at all, and as a machinist I doubt there's anything on those even I would try repairing. The shaft isn't a big deal. But the gear engages the pin via a slot rather than a hole anyway so I doubt that's what you were referring to.
Have you checked this writeup? Sundstrand rebuild It is pretty good and informative. You might get some good ideas there. It varies a bit from what we have in our loaders, but it's still all basically the same.
Regarding the brass plates inside, no they are not the same. One is for the pump and the other for the motor and they must be installed correctly or they won't work. You just need to look for the little notches in the valve slots. The motor has them in all four corners but the pump only has them in two corners. I don't know what it will do if reversed, but it won't operate properly. From the write-up linked above:

So armed with this info, you might re-check your work and make sure it went together correctly on your first try. If one or two of those parts was installed wrong, the drive won't work correctly for sure, and maybe not at all. I would start with the charge pump cover and make sure it's not flipped 180º. Off the top of my head, that seems most likely. Check the link above to see the proper things to look for. If it's not that, I suppose it could be you've transposed those two bronze-faced valve plates inside.
Not sure if this will be helpful yet, but here's my post about a hydrostat rebuild. It's not very informative yet (I'm still in the middle of it), but maybe there's a useful tidbit there anyway.
http://www.skidsteerforum.com/DesktopDefault.aspx?tabid=54&frmView=ShowPost&PostID=92178
At any rate, I'm guessing your repair work is probably OK and the problem is likely to simply be a reassembly error.

I thought in case you haven't got this yet, the service manual from Danfoss (current manufacturer and supplier of Sundstrand stuff I guess) would be helpful too.
http://files.danfoss.com/documents/series 15 transmissions service manual/bln-9646.pdf
The drawings do show the proper orientation of the charge pump cover I'm pretty sure. I think the way it goes is that there is a flat on one of the ears, and that flat points to the control lever. I'm pretty sure about that but not absolutely positive yet. I'll have a look at mine and hopefully it will have some kind of witness mark or stain or something so I can verify this. Dummy me, I didn't take a photo of them before I dug inside and now I wish I had paid better attention. I'll report back what I find, if I find anything.

 

[Mxlord]

I thought in case you haven't got this yet, the service manual from Danfoss (current manufacturer and supplier of Sundstrand stuff I guess) would be helpful too.
http://files.danfoss.com/documents/series%2015%20transmissions%20service%20manual/bln-9646.pdf
The drawings do show the proper orientation of the charge pump cover I'm pretty sure. I think the way it goes is that there is a flat on one of the ears, and that flat points to the control lever. I'm pretty sure about that but not absolutely positive yet. I'll have a look at mine and hopefully it will have some kind of witness mark or stain or something so I can verify this. Dummy me, I didn't take a photo of them before I dug inside and now I wish I had paid better attention. I'll report back what I find, if I find anything.

Thanks for all the info, unfortunately it decided to snow last night and I'm gonna have to wait to work on it. When the skid steer broke it decided to do it in a spot far away from my garage and I have no way to get it back to the garage.

 

[vinito]

Thanks for all the info, unfortunately it decided to snow last night and I'm gonna have to wait to work on it. When the skid steer broke it decided to do it in a spot far away from my garage and I have no way to get it back to the garage.

I verified an important detail about the charge pump cover plate orientation. The left and right sides are not identical on the bench, but it does follow a "rule" which hopefully will make sense.
If you follow the Danfoss/Sundstrand service manual, you will only get one of them correct and the other will be backward. The rule is: on the charge pump cover, the ear with the flat points to the control lever (which is "up" when it's installed in the machine). Since the two drives are powered by opposite ends of the same shaft, this makes sense. In other words, one side is driven in a clockwise direction and the other in a counter-clockwise direction, and flipping the charge pump cover 180º also flips the direction the shaft needs to spin to operate correctly.
Here is a photo illustrating how mine were put together, and presumably yours will require the same orientation:

One interesting thing you can do knowing how this works is that if you ever repower your machine and the rotation of the new engine is the opposite direction from the original, you can just flip the charge pump covers 180º and at least the hydrostats will be set to work just fine. Easy peasy. You'd still have to deal with the hydralic pump, but at least part of it would be simple. Of course a feller prolly oughtta just get a proper motor in the first place, but if you're anything like me and looking at a 50/50 chance of being correct with something, I somehow end up choosing wrong about 95% of the time.
Just in case you're not sure what I'm referring to with all this "flat" talk, here's a picture to illustrate:


So the flat shown in the second picture should be oriented as shown in the first picture. And the "right" and "left" sides I referred to are from the perspective of sitting in the driver's seat of the loader and looking forward.

 

[Mxlord]

I verified an important detail about the charge pump cover plate orientation. The left and right sides are not identical on the bench, but it does follow a "rule" which hopefully will make sense.
If you follow the Danfoss/Sundstrand service manual, you will only get one of them correct and the other will be backward. The rule is: on the charge pump cover, the ear with the flat points to the control lever (which is "up" when it's installed in the machine). Since the two drives are powered by opposite ends of the same shaft, this makes sense. In other words, one side is driven in a clockwise direction and the other in a counter-clockwise direction, and flipping the charge pump cover 180º also flips the direction the shaft needs to spin to operate correctly.
Here is a photo illustrating how mine were put together, and presumably yours will require the same orientation:

One interesting thing you can do knowing how this works is that if you ever repower your machine and the rotation of the new engine is the opposite direction from the original, you can just flip the charge pump covers 180º and at least the hydrostats will be set to work just fine. Easy peasy. You'd still have to deal with the hydralic pump, but at least part of it would be simple. Of course a feller prolly oughtta just get a proper motor in the first place, but if you're anything like me and looking at a 50/50 chance of being correct with something, I somehow end up choosing wrong about 95% of the time.
Just in case you're not sure what I'm referring to with all this "flat" talk, here's a picture to illustrate:


So the flat shown in the second picture should be oriented as shown in the first picture. And the "right" and "left" sides I referred to are from the perspective of sitting in the driver's seat of the loader and looking forward.

Well I looked at the charge pump cover and it is upside down. I never would have thought that would make a difference. Can't wait to try it and see if it works. I've missed driving this thing around. I only paid 500 for it like 8 years ago and put a Kohler command 24hp engine on it, its been the best investment ever.

 

[vinito]

Well I looked at the charge pump cover and it is upside down. I never would have thought that would make a difference. Can't wait to try it and see if it works. I've missed driving this thing around. I only paid 500 for it like 8 years ago and put a Kohler command 24hp engine on it, its been the best investment ever.

Excellent. I hope you didn't mix the valve plates up - since you asked about those I figure you've been inside it. Since you already flipped the charge plate cover around, is it only a 25% chance that those are also switched now or is it still 50/50? hehe. I'm not sure what happens if they are switched, but I figure it will either only work in one direction, not work at all or just be really "weak". But if they are switched the symptom will be obvous and you'll know what to do.
Let us know how it goes.

 

[ColbyArdis]

Excellent. I hope you didn't mix the valve plates up - since you asked about those I figure you've been inside it. Since you already flipped the charge plate cover around, is it only a 25% chance that those are also switched now or is it still 50/50? hehe. I'm not sure what happens if they are switched, but I figure it will either only work in one direction, not work at all or just be really "weak". But if they are switched the symptom will be obvous and you'll know what to do.
Let us know how it goes.

Hello... first post. talking about a Gehl 2600 w/ series 15 U type How do I "prime" (with hydraulic oil) the system before restarting after full tare-down...? Thanks. any tip would be appreciated. Thanks, Colby