Bobcat 753c overfull chain case

   / Bobcat 753c overfull chain case #1  

ladrhog

New member
Joined
Apr 19, 2015
Messages
7
Location
spokane, wa
Tractor
scotts
So long story short I bought a bobcat that was sitting for 8 years with bad electrical. Looks like the alternator fell off while running and fried some wires. Got that all sorted out and got it running. Checked all the fluids before I attempted to start it. The hydro reservoir was low but had fluid. After a quick start and run with no hydraulics I checked the level in the reservoir and it was all gone. I checked the plug up front and fluid came pouring out. So after some research if I am correct the only way to get that much fluid is if the drive motor seals are bad. Is this correct? I am sure I will have a ton more questions.
Thanks in advance.
 
   / Bobcat 753c overfull chain case #2  
Not necessarily the drive motor seals bad, could be, but fluid is going past the motor carrier seal. The carrier is the assembly that bolts to the chain case frame and has shaft that has splines on outside end for drive motor to slide into and has chain drive sprocket on other end inside the chain case. Case drain oil from the drive motor passes through the motor and against the carrier shaft seal then returns to tank passing through a case drain filter before dumping into tank. A plugged case drain filter is the most common cause of this carrier seal failing. High restriction in case drain flow forces the fluid to pass around the carrier seal. The filter could be plugged because previous owner(s) did not replace it as recommended per Bobcat or the drive motor and/or hydrostatic pump are starting to fail sending abnormally high amount of debris through the system.

The seal is fairly easy to replace on the 753, no necessary to remove the carrier. Unbolt and remove the motor, pry out/pull the seal, drive in a new seal (apply Permatex or similar to outer steel ring of seal before installing). Always clean or replace case drain filter with any drive motor or carrier repair.
 
   / Bobcat 753c overfull chain case
  • Thread Starter
#3  
Not necessarily the drive motor seals bad, could be, but fluid is going past the motor carrier seal. The carrier is the assembly that bolts to the chain case frame and has shaft that has splines on outside end for drive motor to slide into and has chain drive sprocket on other end inside the chain case. Case drain oil from the drive motor passes through the motor and against the carrier shaft seal then returns to tank passing through a case drain filter before dumping into tank. A plugged case drain filter is the most common cause of this carrier seal failing. High restriction in case drain flow forces the fluid to pass around the carrier seal. The filter could be plugged because previous owner(s) did not replace it as recommended per Bobcat or the drive motor and/or hydrostatic pump are starting to fail sending abnormally high amount of debris through the system.

The seal is fairly easy to replace on the 753, no necessary to remove the carrier. Unbolt and remove the motor, pry out/pull the seal, drive in a new seal (apply Permatex or similar to outer steel ring of seal before installing). Always clean or replace case drain filter with any drive motor or carrier repair.

Where is the case drain filter located? I would assume the previous owner did not due much maintenance. I am going to change out and clean everything to start fresh. Just trying to figure out the hydraulics before I put new fluid in it.
 
   / Bobcat 753c overfull chain case #4  
Case drain filter is a small metal canister in-line with the hose. Follow the smaller of 3 hoses going to the drive motor is the case drain, follow that hose back from each motor until you find it. One of these maybe fastened directly to bottom of the reservoir.
 
   / Bobcat 753c overfull chain case
  • Thread Starter
#5  
Ok found it. It is directly below the tank. IMG_4155.JPG
 
   / Bobcat 753c overfull chain case
  • Thread Starter
#6  
Could someone tell me how to use the aux hydraulics and what the switches on the handles are for. I have a thumb and trigger switch for both handles. Thanks
 
   / Bobcat 753c overfull chain case #8  
Could someone tell me how to use the aux hydraulics and what the switches on the handles are for. I have a thumb and trigger switch for both handles. Thanks

Thumb switch on right handle is for momentary hydraulics to front couplers is bi-directional. Typically used for cylinder operations. The trigger switch on right handle is for constant flow (detent) one direction only, used for hydraulic motor attachments. To activate these: The upper front panel has "AUX" button with 2 small indicator lights. Push the button once and one light comes on, this activates the thumb switch. Push button again and both lights come on, this activates the Right front trigger for detent function.
Trigger switch on Right handle is horn if equipped, and left trigger is for rear auxiliary hydraulics if equipped.
 
   / Bobcat 753c overfull chain case
  • Thread Starter
#9  
Update.

I put in a new case drain filter and filled the hydraulics. It worked great until it overheated. Stuck thermostat.
After screwing with that figured I'd check hydro oil. None in the tank. So it is leaking into the chain case with the machine off. I am going to drain the chain case and pull a top cover and try to see what side is leaking. I'll add oil and look for the leak with the chain case empty.
 
   / Bobcat 753c overfull chain case
  • Thread Starter
#10  
IMG_4324.JPG
Found the problem. Bad seal
 
 
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