My 732 is somehow dumping all it's hydraulic fluid into the chain case. It overfills and pushes out the axle seals. I was trying to get some work done with the blasted thing today and filled the reservoir and within 5 minutes it all had run into the chain case. I don't understand how this is happening, any ideas??? I have already replaced the seals between the wheel motors and the chaincase.
732 Hydraulic mystery problem
- Thread starter schmelvy
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- Dec 17, 2009
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- 239
The only way this can happen is for your drive motor seals to go. The fluid then runs into the reduction gearbox and from there into the chain case. Hate to say it but your drive motors will need to come out for repairs.
getting the drive motors out is no problem, not sure about replacing the seals though. are the seals serviceable or will they have to go to the hydraulic shop?
The bad seals will be in the reduction box, not the motor. The motors have an open side where the dog bone shaped drive sprocketcomes out, the reduction box has a seal for this ara to keep it out of the chain case.
The seals can be done at home, drill a small hole in the seal and screw a self tapping screw into it and lever out with pliers, wash the metal filings out once the seals is out and tap a new one in. Look at this pic to see it: https://www.tractorbynet.com/forums...ts-012-jpg?s=caf9c536e30cdf29c21c3d916e0cb837
The black seal on the right is the one that will be leaking, check the shaft for play too, if it moves, your bearings are bad and a new seal will not do anything.
those are the seals I just replaced, they only have a couple hours of run time on them. hence the mystery continues. I think I will pull it apart to check the play in the bearings again, but I really think there must be something else going on as the seals I replaced really didn't look bad.
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Any other ideas?
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- Dec 17, 2009
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I've never actually had mine off so I don't know exactly what it looks like in there but I would imagine there should be some kind of a seal in the motor itself that keeps it from draining all the oil out... https://www.bobcatpartsonline.com/#/catalogBrowser?path=%2F0000-Loaders%2F0000-732%2F0000-5000M11001%20%26%20Above%2F0005-Hydrostatic%20System%2F0004-Hydrostatic%20Motor Item 3 and 28 would be high on the list of my suspects here, but again never having been inside one of these motors I'm just shooting in the dark here. Another thought would be if those seals you replaced are directional and they may have been put in backwards... Again just an idea.
the seals are in right. I was on the same train of thought though, I looked at the exploded view of the wheel motor as well, I guess I will just replace all the O-rings in there and try it again. I just cant see anywhere else it could be . I have literally been fighting this for years, It has now just gotten so bad I can no longer use the machine.
There really is no seal in the motor to hold back the oil tha leaks out.
You have the high pressure seals where the fluid enters and goes to the valve plate to direct fluid to the required holes in the geroler. The other side of the geroler has nothing stopping fluid leaking past and into the dog bone shaped gear setup. As the geroler star moves around, it kind of wobbles, so you can't use a normal lip seal. Thats why the dog bone has rounded corners on the gears, so it can wobble around and be covered in oil when it does so. This is where the reduction box seal holds the fluid back.
I wonder if the issue could be the return lines, they have no filters, but if there was a restriction, it could be the cause?
I'd even try taking the return lines off and seeing what sort of flow you are geting. Without load, there should be little fluid coming out, under load you will get more. If one is pouring out, there may be an issue with that motor.
I would think if there was a return line problem, it would affect the functionality of the drive motor in some way? not sure. the machine drives just fine though. just somehow is emptying the hydraulic into the chaincase in short order. Im going to pull it apart again but not very optimistic at this point. I am ready to junk the stupid thing. no logical reason for whats happening that I can see.
The return line just pumps the “waste” oil back to the tank, so I don't think it would make it run poorly
Try taking the fitting off and seeing how much fluid comes out of the motor when jus t free wheeling, then you can see how much comes out when you apply the brake and push against it a bit (putting it under load)
Finally got a chance to tear into it, had car and truck repairs that took priority. It used 5 gallons of hydraulic just to get it into the shop from 60 ' away. (when I say used, I mean pumped into the chain case) I didnt try pulling any lines off to test as I am going to go broke buying fluid just trying to move this lemon around. At any rate, with the wheel motors off, it looks fine. The seals are basically new, not more than a couple of hours on them. I replaced them a while back hoping to fix the problem, which at that time was not nearly as drastic as it is now. I could still use the machine, losing some fluid into the chain case. after replacing the seals, it seemed to be maybe a little better, for a short time, but now much, much worse. At any rate, the seals look fine. The bearings are fine, all the lines including the relief lines drained a normal amount of fluid so I dont think any of them are plugged. It is forcing high pressure fluid unabated into the chain case at a high rate, but I cant see where. Is there any other place where the two systems intersect?
Hotrod1830
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- Sep 14, 2010
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If you are sure the seals are good, that would make me look at the case drains/return. If they are restricted and pushing fluid out of the seals, you may have to replace the seals again. remember, the hydro system can generate pressures of around 5000 psi.
Is it only one motor leaking or both? If both, it would also point to a restriction in the case drain. If only one, you may have a worn motor on that side.
Is it only one motor leaking or both? If both, it would also point to a restriction in the case drain. If only one, you may have a worn motor on that side.
It looks like the case drains are clear, I can push low pressure air through them. (vents back through the tank/I looked up the diagram) I dont know if it is one motor or both. The seals look good, but I suppose I will have to pull one or both to examine them as you said they are possibly damaged due to extreme pressure. I think I am going to clean up the motors and pull them apart. there has to be a reason, I just hope I can find it.
quick correction, I was passing low pressure air through the case drains, but with both motors off, it was venting out the other side, in any case, the lines are clear through that section of the system.
update-I pulled a seal out. It was certainly in there correctly, no apparent damage. gotta love ruining a $30 seal for no good reason. kind of wondering how its pushing that much fluid through without damage to the seals I have to be missing something. this just dosent add up.
question on the seals- Are the bobcat factory seals different from the average oil seal? the Bobcat part is#6513588 not wanting to have to order high priced seals from the bobcat dealer and then having to wait for them to come in, I had my local part supplier X reference the old ones, came up with CR#25091 I havent been able to find any information on the bobcat seal, but the CR seal is only rated for 10PSI I am thinking the bobcat seal maybe capable of holding back a higher pressure. however, with that being said it looks like some aftermarket suppliers offer a very standard looking seal as a replacement for the bobcat part. Has anyone else had experience with these seals or have any insight on whether there is any difference between the bobcat seal and the aftermarket seal? Thank you all for your responses, I really appreciate it.
Hotrod1830
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Not sure about the seals. If in doubt, stick with bobcat parts.
You can tee in a gauge on the return/case drain hose and check pressure during operation. You would have to check a manual for max pressure, as I dont remember the spec off hand. the only manual I have is for a 553. no spec is given.
can you operate the machine with the chain case cover removed and see if you can see if it is one motor or both leaking?
You can tee in a gauge on the return/case drain hose and check pressure during operation. You would have to check a manual for max pressure, as I dont remember the spec off hand. the only manual I have is for a 553. no spec is given.
can you operate the machine with the chain case cover removed and see if you can see if it is one motor or both leaking?
no way to get the cover off without basically tearing the whole machine down and then reassembling without the cover in place to test, way more work there than what it would be worth good idea to tee in a gauge there, I think I will try that if I dont find anything in the wheel motors, Im going to clean them up and pull them apart to inspect them and replace the O-rings since I have them off anyway. thanks
