I'm buying a 753 G from an old dude for $900. 2500 hours. The battery was dead when I looked at it, it's charging now. He said it runs good. I'll verify before I actually buy. previous owner took it to a bobcat service place to have the right motor replaced. He said shortly after it started hydraulic fluid into the chain box. In one of these threads I read something about about a motor carrier seal, I think. Thoughts?
New to me 753 hydraulic leak
- Thread starter icecheez
- Start date
The motor carrier seals are the normal cause of fluid going into the chain case.
If this is the problem I would actually replace both sides since you don’t know if the one was replaced with the motor or may have been damaged or the other side has just gotten old and failed.
If this is the problem I would actually replace both sides since you don’t know if the one was replaced with the motor or may have been damaged or the other side has just gotten old and failed.
I’m not sure what shim they are talking about.
The motor carrier seals are a common problem as they just get old and fail. Not too hard to replace them.
Here is a link to the parts catalog. You can take a look at your specific machine and see the schematics for the motor carrier:
https://partscatalog.bobcat.com/
Thanks! Hopefully this is the problem.
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I do not believe that the 753 came with a hydraulic fan. It is a belt driven fan.
The fan gear box takes gear oil and can only leak out if the seals go bad or the fill plug is loose or missing.
Hydraulic oil can not get into the fan gear box. It does take gear oil in the 80W range but again there is no way for hydraulic oil to get in there. The fan is belt driven and a closed gear box. Oil can only leak out of it.
Oil can leak onto the fan and gear box from the oil cooler that is above it but even then it could not make its way into the fan gear box.
Ok, great. he might be senile. Hopefully the first theory was correct. I went there yestday to start it. he made it sound like it was sitting there a Year, but it's been much longer. it is very low on hydraulic fluid. needs a new battery. i did get it to turn on, not turn over. I'm going back today a little oil and a battery.
You would be able to tell if there was oil leaking into the chain case by checking the chain case oil level.
There is a plug on the front of the machine in the middle, face, of the chain case. This is the inspection plug also used to pump the old oil out. New oil is added to the bottom of the plug hole. If the machine is on level ground and this plug is removed, very little to no oil should come out of the plug. If oil has leaked into the chain case oil will gush out of the hole.
Keep in mind though that water just from condensation can also fill the chain case especially when a machine sits for a long time.
He might be senile if the $900 dollar price tag is correct. You could probably get that for it in scrap let alone parting it out.
There is a plug on the front of the machine in the middle, face, of the chain case. This is the inspection plug also used to pump the old oil out. New oil is added to the bottom of the plug hole. If the machine is on level ground and this plug is removed, very little to no oil should come out of the plug. If oil has leaked into the chain case oil will gush out of the hole.
Keep in mind though that water just from condensation can also fill the chain case especially when a machine sits for a long time.
He might be senile if the $900 dollar price tag is correct. You could probably get that for it in scrap let alone parting it out.
I got it started, put fluid in, and oil on the right side. it seems to be coming from the forward right corner squeezing through the gasket. so, pump the oil down so it won't out, replace the seals, add oil, should be good to go. the engine sounded real good, started right up after i replaced the battery.
Dave the Ozzie
Well-known member
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- May 23, 2024
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- 51
If you feel that the chain case is filling from a leaking motor seal then my first check would be the inline sintered metal filters on the bleed off lines from each motor back to the suction line on the hydraulic tank. I’m thinking that if they’re blocked then it could put pressure inside the motor where it shouldn’t and leak past the shaft seal. Just a thought. 
I just had a thought. When I got it started, after adding about 5.5 gallons oil, I didn't try moving it as there wasn't enough oil yet. But it still all pumped out, pretty quickly, too. Near as I could tell, it was coming out from a corner of the cover of the chain case. is there pressure to the motors even when still? Or maybe the linkage is out of adjustment or something? either way, it didn't act like it tried to move before the motor auto shut off.
Dave the Ozzie
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- Joined
- May 23, 2024
- Messages
- 51
There’s no flow/pressure at the motors when the hydrostatic pumps are in the “neutral” position. If you think that the linkage adjustment could be out then try putting the machine on jack stands to get the weight off the tyres. If the brake is still operational then the brake solenoid also must be engaged to have locking puck release from the discs so the wheels can turn freely if the motors are receiving fluid.
Are you 100% sure that fluid is actually coming from the chain case and not from a blown hose on top of the case?
I looked around for a wet hose, the only wetness I could find was from the forward right corner in the cover underneath the seat
The motors are the only way in to the chain case right? one of the brackets that engages the limit switch for the brakes was missing. So it wouldn't surprise me he was fooling around trying to figure it out.
I've got the seals, will check the sintered filters tomorrow, after pumping out the excess oil from the case. I guess while I have the motors out, I'll run it for long enough to see if there's excessive leakage. And I'll block it up so all four wheels are off the ground.
