631 chaincase full of hydraulic oil

[alexvbugman]

I've replaced one drive motor and rebuilt other and am still losing hydraulic fluid into the case, I can't figure it out. Any ideas?

 

[mmsllc]

I think the seals are located inside the part that the motors mount to. I have heard of this issue before on here. You have the right idea though. I would suggest going to BOBCAT to get a parts diagram to better illustrate my point. Chances arevthatbthey will also have the correct seals, too.

 

[Tazza]

I think the seals are located inside the part that the motors mount to. I have heard of this issue before on here. You have the right idea though. I would suggest going to BOBCAT to get a parts diagram to better illustrate my point. Chances arevthatbthey will also have the correct seals, too.

If you have a reduction box on the chain case, you probably have seals that hold the oil in the motor and not let it go into the chain case.

 

[alexvbugman]

If you have a reduction box on the chain case, you probably have seals that hold the oil in the motor and not let it go into the chain case.

No reduction box, the motors are direct to the sprockets. I'm losing bout gallon per hour, maybe more.

 

[Tazza]

No reduction box, the motors are direct to the sprockets. I'm losing bout gallon per hour, maybe more.

Sounds like one of the seals is still bad.
The case drain line could be plugged. This will allow pressre to build up and pushes past the seal.

 

[mmsllc]

Sounds like one of the seals is still bad.
The case drain line could be plugged. This will allow pressre to build up and pushes past the seal.

For the life of me, I could not come up with "reduction gear box". It does sound like a seal is still leaking. I would suggest complete / thorough inspection of all parts that are associated with sealing fluid in the motors. It could be something like a worn shaft, like a groove cut into the shaft. Or a small hairline crack in one of the travel motor housings. Lastly, try only using BOBCAT seals. I swear there is sometimes a big difference in quality of their parts versus cheaper ones. NOT always, but generally speaking, they are different on some level or another.

 

[mmsllc]

For the life of me, I could not come up with "reduction gear box". It does sound like a seal is still leaking. I would suggest complete / thorough inspection of all parts that are associated with sealing fluid in the motors. It could be something like a worn shaft, like a groove cut into the shaft. Or a small hairline crack in one of the travel motor housings. Lastly, try only using BOBCAT seals. I swear there is sometimes a big difference in quality of their parts versus cheaper ones. NOT always, but generally speaking, they are different on some level or another.

Do 631's have case drain filters, if the 743's do not? Just a curiosity.

 

[Imho]

Do 631's have case drain filters, if the 743's do not? Just a curiosity.

Based on my limited knowledge gained from reading every post related to overfull chaincases, and having just successfully replaced the seals where the motor mounts to the reduction box on my 743, these are the main things I've learned: 1. The only way for hydraulic fluid to enter the chaincase is via the seal on either the reduction box or motor carrier (it doesn't matter which). 2. If case drain filters are fitted to your model, and they are clogged, it could cause excessive case drain pressure and force hydraulic fluid past the seal, or the seal could be damaged (the question is why?), or just worn out. Wear can sometimes be hard to spot, though. 3. Failure of other seals in the motor, or the motor itself, could also cause excessive pressure (given you've replaced/rebuilt your motors, this is unlikely). For the sake of ~$100 in parts, including the case seal, quad ring seal, and o-ring, I'd replace all three on both sides. I'm pretty confident this would solve your problem, but check the case drain filters (if fitted) otherwise it will probably just happen again. There is a post on this forum with pics, and a post with the process required to replace the seals.

 

[Imho]

Based on my limited knowledge gained from reading every post related to overfull chaincases, and having just successfully replaced the seals where the motor mounts to the reduction box on my 743, these are the main things I've learned: 1. The only way for hydraulic fluid to enter the chaincase is via the seal on either the reduction box or motor carrier (it doesn't matter which). 2. If case drain filters are fitted to your model, and they are clogged, it could cause excessive case drain pressure and force hydraulic fluid past the seal, or the seal could be damaged (the question is why?), or just worn out. Wear can sometimes be hard to spot, though. 3. Failure of other seals in the motor, or the motor itself, could also cause excessive pressure (given you've replaced/rebuilt your motors, this is unlikely). For the sake of ~$100 in parts, including the case seal, quad ring seal, and o-ring, I'd replace all three on both sides. I'm pretty confident this would solve your problem, but check the case drain filters (if fitted) otherwise it will probably just happen again. There is a post on this forum with pics, and a post with the process required to replace the seals.

Ok, having had a look at the parts manual for the 631, you are correct, there is no seal, just an o-ring between the drive motor and the chaincase, and no case drain hose. So, that pretty much exceeds any experience I have. Could you unbolt the motor and run it to see if hydraulic fluid is being pumped out of the motor? Given the design, I can't see how fluid can be allowed to exit the shaft side of the motor without filling the chaincase.

 

[Tazza]

Ok, having had a look at the parts manual for the 631, you are correct, there is no seal, just an o-ring between the drive motor and the chaincase, and no case drain hose. So, that pretty much exceeds any experience I have. Could you unbolt the motor and run it to see if hydraulic fluid is being pumped out of the motor? Given the design, I can't see how fluid can be allowed to exit the shaft side of the motor without filling the chaincase.

Removing the motor from the machine and running it won't always tell you a lot, you really need for it to be loaded to know for sure how it will operate. If the leak is bad enough, it will work out of the machine though.