I recently purchased a 963 bobcat, knowing it had hydraulic leaking in the chain case. The guy I bought it from said he replaced both drive motor shaft seals and it didn't fix the problem, the motors are strong and pull straight. It leaks about 1gph when at idle, not working and 2gph when working it doesn't seem to leak when the machine is off after it has lost pressure. He believes it to be an internal drive motor seal and the motors need to be rebuilt, it seems to me there would be a loss of power or something wrong with their operation - am I correct here? Is there somewhere else hyd. oil can get into the chain case? Any help would be greatly appreciated...
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I don't know what motors that machine runs, but i'd check the usual things. Case drain filters if fitted. They plug up and can cause excessive case drain pressure that pushes past the seal.
Smaller machines actually when this happens it fills the chain case. It gets past a carrier seal and fills it up.
Start with case drain filters, that would still push past shaft seals or even push the seals out if it's high enough.
Smaller machines actually when this happens it fills the chain case. It gets past a carrier seal and fills it up.
Start with case drain filters, that would still push past shaft seals or even push the seals out if it's high enough.
Thanks Tazza, I'll check it out and get back to you. Maybe this info will help while I check the case drain filters; the machine is a 99 model and only has 1100hrs, It starts leaking soon as you start it up without engaging the hydraulics.I don't know what motors that machine runs, but i'd check the usual things. Case drain filters if fitted. They plug up and can cause excessive case drain pressure that pushes past the seal.
Smaller machines actually when this happens it fills the chain case. It gets past a carrier seal and fills it up.
Start with case drain filters, that would still push past shaft seals or even push the seals out if it's high enough.
I saw only one case drain filter by the hydrostatic controller and it was clean, the previous owner may have cleaned/replaced trying to figure it out. I also pulled both drive motors out of the housing about 3/4" with the lines attached, started the engine and neither were leaking. Do you think it could be a carrier seal as you mentioned above, is there a way to test them?? Also, I read somewhere about hyd. brake lines in the chain case; could this be an issue and is there a way to test??I don't know what motors that machine runs, but i'd check the usual things. Case drain filters if fitted. They plug up and can cause excessive case drain pressure that pushes past the seal.
Smaller machines actually when this happens it fills the chain case. It gets past a carrier seal and fills it up.
Start with case drain filters, that would still push past shaft seals or even push the seals out if it's high enough.
If it has carrier seals, i'd change them. Age can make them fail, and the filter may have been replaced like you said.I saw only one case drain filter by the hydrostatic controller and it was clean, the previous owner may have cleaned/replaced trying to figure it out. I also pulled both drive motors out of the housing about 3/4" with the lines attached, started the engine and neither were leaking. Do you think it could be a carrier seal as you mentioned above, is there a way to test them?? Also, I read somewhere about hyd. brake lines in the chain case; could this be an issue and is there a way to test??
I don't know what type of brake these run, if it is hydraulic, it is very possible it is the cause.
Thank you Tazza for your help; I'll check it out and posts what I find.If it has carrier seals, i'd change them. Age can make them fail, and the filter may have been replaced like you said.
I don't know what type of brake these run, if it is hydraulic, it is very possible it is the cause.
Hey Tazz,and BC. There is no "carrier seals" in a 963 it has a gear box drive. It does have spring applied, hyd released brakes. BUT. The brakes r inside the chaincase. The 963 uses a piston style motor, not a gerolor. U measured the lose of hyd oil. Try having the machine running, with the parkbrake on versus the park brake off, without moving the machine. It could be just a hose inside the chaincase is leaking.Thank you Tazza for your help; I'll check it out and posts what I find.
Hey Biggie, thanks for all the good info guys, you've been a big help, maybe I can return the favor one day or help someone else. I just finished putting it back together about an hour ago. It was a brake line in the chain case, I got lucky this time. I purchased it for 7400 + 500 for fuel to and from S. Carolina, now a total of 8400 in it. It's in great condition but, there's still a few things I need to do; probably always will. Thanks again for help!Hey Tazz,and BC. There is no "carrier seals" in a 963 it has a gear box drive. It does have spring applied, hyd released brakes. BUT. The brakes r inside the chaincase. The 963 uses a piston style motor, not a gerolor. U measured the lose of hyd oil. Try having the machine running, with the parkbrake on versus the park brake off, without moving the machine. It could be just a hose inside the chaincase is leaking.
Nice job.Hey Biggie, thanks for all the good info guys, you've been a big help, maybe I can return the favor one day or help someone else. I just finished putting it back together about an hour ago. It was a brake line in the chain case, I got lucky this time. I purchased it for 7400 + 500 for fuel to and from S. Carolina, now a total of 8400 in it. It's in great condition but, there's still a few things I need to do; probably always will. Thanks again for help!
Good to know there are no carrier seals, hopefully i'll remember for next time.
