1996 Bobcat 753 Turning Issue - Serious Problem

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Arley

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May 16, 2011
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6
I just bought a fixerup Bobcat 753 and I'm perplexed. It will sort of drive staight but actually only turns right with full power. When I steer left it feels like it is fighting me. The engine loads down and it goes no place. It only seems to opperate properly when in a full right turn as the left has a strong forward and the right has a strong reverse. All the mechanical linkage looks ok and the centering adjustment looks good. Any help would be appreciated. Thanks...Wayne
 

Tazza

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Dec 7, 2004
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16,829
Its possibly a drive motor issue, you can easily swap them, if the problem moves, its the motor, if not its the pump.
 
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Arley

Member
Joined
May 16, 2011
Messages
6
Its possibly a drive motor issue, you can easily swap them, if the problem moves, its the motor, if not its the pump.
I decided to pull the Right Drive Motor apart and it looks great. I'll put a kit in it but there is no mechanical damage and no marks or scoring on any of the parts. There was however a small amount of brown crud under one of the rings so I don't feel bad about tearing it down. I'll go ahead and put a kit in the Left Drive Motor just to be sure there is no buildup of crud in it. Now I'm pretty sure my problem was not the drive motor. The chain drive seems fairly tight and the electric brake is working properly. I'm starting to think my problem is in the main Tandem Drive Pump but I'd like to put things back together and give it another test before I pull the Engine and Drive Pump. Questions: 1)What is the best way to completly drain the Hyd Tank. I have the right drive removed so the hoses are slowly dripping. I would like to remove the tank and clean it out) 2) Should I remove the 2 inline filters and clean them out? If so what is the procedure for cleaning them? 3) Is there a kit available for the Tandem Drive Pump? I don't want to pay $2000.00 for a rebuilt drive. Is there anything unusual about tearing down the Tandem Pump? Thanks, Arley
 
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Arley

Member
Joined
May 16, 2011
Messages
6
I decided to pull the Right Drive Motor apart and it looks great. I'll put a kit in it but there is no mechanical damage and no marks or scoring on any of the parts. There was however a small amount of brown crud under one of the rings so I don't feel bad about tearing it down. I'll go ahead and put a kit in the Left Drive Motor just to be sure there is no buildup of crud in it. Now I'm pretty sure my problem was not the drive motor. The chain drive seems fairly tight and the electric brake is working properly. I'm starting to think my problem is in the main Tandem Drive Pump but I'd like to put things back together and give it another test before I pull the Engine and Drive Pump. Questions: 1)What is the best way to completly drain the Hyd Tank. I have the right drive removed so the hoses are slowly dripping. I would like to remove the tank and clean it out) 2) Should I remove the 2 inline filters and clean them out? If so what is the procedure for cleaning them? 3) Is there a kit available for the Tandem Drive Pump? I don't want to pay $2000.00 for a rebuilt drive. Is there anything unusual about tearing down the Tandem Pump? Thanks, Arley
Well... both the L & R Drive Motors are now on the bench. They are clean and ready for new seals & rings. I noticed that the Left Motor (was working properly) had the same amount of redish brown crud under the brass ring as the left motor. Both motors appear to be undamaged with no scoring and had no damaged or broken seals. I did notice that the Left Motor (working properly) was easy to turn on the bench while I could not turn the Right Motor (not working properly) and that when I pulled the lines on the Left Motor (working) there was a nice flow of fluid out of the lines while the Right (not working properly) Motor's lines just dripped fluid for the longest time. I don't know if any of this information is significant but I would appreciate some feedback. Arley
 

Tazza

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Dec 7, 2004
Messages
16,829
Well... both the L & R Drive Motors are now on the bench. They are clean and ready for new seals & rings. I noticed that the Left Motor (was working properly) had the same amount of redish brown crud under the brass ring as the left motor. Both motors appear to be undamaged with no scoring and had no damaged or broken seals. I did notice that the Left Motor (working properly) was easy to turn on the bench while I could not turn the Right Motor (not working properly) and that when I pulled the lines on the Left Motor (working) there was a nice flow of fluid out of the lines while the Right (not working properly) Motor's lines just dripped fluid for the longest time. I don't know if any of this information is significant but I would appreciate some feedback. Arley
The drive motors should not be easy to turn by hand. Its normal to have to use pliers to hold the shaft to get it to rotate, so don't be concerned there.
Parts for the pump are available if you are confident you can do the work. loader parts source have new rotating groups and wear plates available. But don't do anything about that till you open the pump up. You may be able to get away with flattening the wear plates, we'll get to that depending on what you find if the motors still don't work.
As for draining oil, i hook a hose to my aux hydraulic lines and pump it into a bucket at idle. As soon as it starts to spit i shut down. Some say this can cause pump damage, but i have never had a problem as there is still oil residue in the pump, its your call if you do it this way or not.
The drive pumps are pretty simple. I would make sure i tried swapping motors before you condem it to being damaged.
Yes, i'd change or at least clean the case drain filters (inline filters).
 
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Arley

Member
Joined
May 16, 2011
Messages
6
The drive motors should not be easy to turn by hand. Its normal to have to use pliers to hold the shaft to get it to rotate, so don't be concerned there.
Parts for the pump are available if you are confident you can do the work. loader parts source have new rotating groups and wear plates available. But don't do anything about that till you open the pump up. You may be able to get away with flattening the wear plates, we'll get to that depending on what you find if the motors still don't work.
As for draining oil, i hook a hose to my aux hydraulic lines and pump it into a bucket at idle. As soon as it starts to spit i shut down. Some say this can cause pump damage, but i have never had a problem as there is still oil residue in the pump, its your call if you do it this way or not.
The drive pumps are pretty simple. I would make sure i tried swapping motors before you condem it to being damaged.
Yes, i'd change or at least clean the case drain filters (inline filters).
Well....at this point I've got both the motors apart on the bench so I'll have to get a couple of kits and put them back together before I can continue testing. I cleaned the inline filters (with brake cleaner and air pressure) and found a fair amount of brass particles (no doubt from the drive motors) in each filter. I even removed the hyd. tank and flushed it out just to be sure it wasn't filled with sludge. It was pretty clean inside. Thank you for your help thus far. We will see how it works when I get the motors rebuilt. Arley
 
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Arley

Member
Joined
May 16, 2011
Messages
6
Well....at this point I've got both the motors apart on the bench so I'll have to get a couple of kits and put them back together before I can continue testing. I cleaned the inline filters (with brake cleaner and air pressure) and found a fair amount of brass particles (no doubt from the drive motors) in each filter. I even removed the hyd. tank and flushed it out just to be sure it wasn't filled with sludge. It was pretty clean inside. Thank you for your help thus far. We will see how it works when I get the motors rebuilt. Arley
Resolution: Thanks for your help.... I rebuilt both drive motors and everything works as it should. I still have a few minor repairs to complete but at least the drive issue is behind me.
 

Tazza

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Staff member
Joined
Dec 7, 2004
Messages
16,829
Resolution: Thanks for your help.... I rebuilt both drive motors and everything works as it should. I still have a few minor repairs to complete but at least the drive issue is behind me.
Good to hear its up and running.
 
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