753 drive motor leak(s). Newby...

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Graham

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Feb 9, 2006
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I have just bought a 753 with 1500 hours everything appears to work except there is a huge hydraulic leak from the chaincase. Apparently both drive motors are leaking. The seller is going to pay for the repair as I bought a "Bobcat ready to work". But I have a few questions worrying me. If the dealer reseals the drive motors what is the likelyhood of them leaking again quite soon? Because something has caused those seals to leak, either dirt or bearing or shaft wear. Would it be in the drive motors or the seals between the drive motor and the carrier? How concerned, about repeat leaking problems, should I be? A new drive motor is $999.76 and a reseal kit is $80.00 If the seller wasn''t paying for the repair I would be tempted to pull both motors and try to reseal them. Maybe I will have to do this in the future!?!?!? Thanks, Graham.
 

sterlclan

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May 1, 2004
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If a bobcat dealer or a good hydralic shop does the work i doubt they would reseal something that is just going to fail odds are if the shaft or bearing is bad they would let you know first good luck and welcome to the forum Jeff
 

Tazza

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If a bobcat dealer or a good hydralic shop does the work i doubt they would reseal something that is just going to fail odds are if the shaft or bearing is bad they would let you know first good luck and welcome to the forum Jeff
The leak will be from the motor, it will have nothing to do with the gear box (you refered to it as the carrier) The gear box has no oil pressure against it, only the motor. You could pull the motors off the gear box and test to see what one is leaking. Block the loader remove 1 motor leaving it connected and push the steering lever backwards or forwards. You may need to run if for a little while as there will be no load and the oil won't want to come out very fast. I would bet only one motor is leaking, but you could get both done for peace of mind.
I think its unusual for a seal to go so fast, but it may have been a dud seal. You can take the motor to Bobcat and get them to re-kit it for you, they can tell you if there is any abnormal wear too. You can re-kit it yourself, but you must re-time it correctly, you can't simply slap it back together.
Good luck, let us know how you go!.
 

Luthor

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The leak will be from the motor, it will have nothing to do with the gear box (you refered to it as the carrier) The gear box has no oil pressure against it, only the motor. You could pull the motors off the gear box and test to see what one is leaking. Block the loader remove 1 motor leaving it connected and push the steering lever backwards or forwards. You may need to run if for a little while as there will be no load and the oil won't want to come out very fast. I would bet only one motor is leaking, but you could get both done for peace of mind.
I think its unusual for a seal to go so fast, but it may have been a dud seal. You can take the motor to Bobcat and get them to re-kit it for you, they can tell you if there is any abnormal wear too. You can re-kit it yourself, but you must re-time it correctly, you can't simply slap it back together.
Good luck, let us know how you go!.
It may only be a bad hose, have you checked?
 

Graham

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Feb 9, 2006
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9
It may only be a bad hose, have you checked?
Aren't the drive motor hoses external to the chaincase? Are any hoses in the chaincase? I don't think so but I may be wrong. Thanks for all of your responses. Graham.
 

Graham

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Feb 9, 2006
Messages
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The leak will be from the motor, it will have nothing to do with the gear box (you refered to it as the carrier) The gear box has no oil pressure against it, only the motor. You could pull the motors off the gear box and test to see what one is leaking. Block the loader remove 1 motor leaving it connected and push the steering lever backwards or forwards. You may need to run if for a little while as there will be no load and the oil won't want to come out very fast. I would bet only one motor is leaking, but you could get both done for peace of mind.
I think its unusual for a seal to go so fast, but it may have been a dud seal. You can take the motor to Bobcat and get them to re-kit it for you, they can tell you if there is any abnormal wear too. You can re-kit it yourself, but you must re-time it correctly, you can't simply slap it back together.
Good luck, let us know how you go!.
Tazza, I did not know that the drive motor had to be timed. I'll have to study this device to get some better understanding. I really appreciate all the responses, thanks guys, Graham.
 

Tazza

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Tazza, I did not know that the drive motor had to be timed. I'll have to study this device to get some better understanding. I really appreciate all the responses, thanks guys, Graham.
Graham, if you decide to repair the motors yourself, call Bobcat and talk to their service department. They will give you all the information you need on timing and how to go about it. Never be afraid to pick their brains, they are always happy to help.
If you run in to trouble, just take it in and they will re-assemble it for you, i'm not sure how much it will cost to do, but from what i have heard, its not much.
 

Graham

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Feb 9, 2006
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Graham, if you decide to repair the motors yourself, call Bobcat and talk to their service department. They will give you all the information you need on timing and how to go about it. Never be afraid to pick their brains, they are always happy to help.
If you run in to trouble, just take it in and they will re-assemble it for you, i'm not sure how much it will cost to do, but from what i have heard, its not much.
You may all have friendlier dealers!! I have spoken to the dealer this morning and he admitted they don't know which one is leaking but to cover themselves they just reseal BOTH drive motors. He said that there is no timing involved with the drive motor but the gears all had to come apart in the chaincase. I just received a service manual and the manual claims you just unbolt the drive motor from the "carrier" and just bolt it back on. The only gear I see is not a gear but a chain sprocket. The manual refers to another manual (Hydrostatic Motors Repair Manual) for information on replacing the seal in the drive motor. But it appears the outer carrier seal should also be replaced. This all appears to be done without having to go into the chaincase. It actually looks pretty simple according to the manual. Graham.
 

Tazza

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You may all have friendlier dealers!! I have spoken to the dealer this morning and he admitted they don't know which one is leaking but to cover themselves they just reseal BOTH drive motors. He said that there is no timing involved with the drive motor but the gears all had to come apart in the chaincase. I just received a service manual and the manual claims you just unbolt the drive motor from the "carrier" and just bolt it back on. The only gear I see is not a gear but a chain sprocket. The manual refers to another manual (Hydrostatic Motors Repair Manual) for information on replacing the seal in the drive motor. But it appears the outer carrier seal should also be replaced. This all appears to be done without having to go into the chaincase. It actually looks pretty simple according to the manual. Graham.
As far as i was aware, you just un-did the 4 bolts on the motor and pulled it straight out, no bolts inside the chain case. The sprockets inside the chain case are not directally connected the the motor.... Unless the bolt that holds the park brake discs is connected to the motor.....
As for the “Hydrostatic Motors Repair Manual” this will cover the timing and how to replace the seals. I have never priced this manual, it may be a better option for you to give the motor and seal kit to your dealer and say FIX. Unless you want to give it a go yourself, they aren't really that complicated, you just need to get the timing rite and use lots of oil in re-assembly ooh and of course, keep it all clean!!!
 

Graham

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Feb 9, 2006
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As far as i was aware, you just un-did the 4 bolts on the motor and pulled it straight out, no bolts inside the chain case. The sprockets inside the chain case are not directally connected the the motor.... Unless the bolt that holds the park brake discs is connected to the motor.....
As for the “Hydrostatic Motors Repair Manual” this will cover the timing and how to replace the seals. I have never priced this manual, it may be a better option for you to give the motor and seal kit to your dealer and say FIX. Unless you want to give it a go yourself, they aren't really that complicated, you just need to get the timing rite and use lots of oil in re-assembly ooh and of course, keep it all clean!!!
Okay it is fixed and here is what I found out. I jacked up the rear a few inches and removed both rear wheels. Removed both side covers. marked the top pressure hose so as not to put them back on the wrong fittings. Removed all 3 hoses on each motor. Removed the 4 retaining bolts and slid out both motors. On the left side the seal on the carrier shaft looked just fine but I replaced it with the newer design. To do this I removed the seal and retainer with a screw-in seal puller. The seal looks like one piece but the seal is a seperate part. I used the old retainer part to press the new seal unit into place. The newer design is one piece. Need to be careful not to damage the seal as it is a very tight fit. On the right side I found the seal had fallen out of the retainer and was not even on the shaft. After re-installing the motors I ran the machine to pump out all the old oil, then re-filled with new oil. Then re-installed the 6 hoses to the motors with new o-rings. It appeared to have no leaks so I drove it around for 40 minutes the hydraulic oil level had not changed (allowing for heat expansion). That's it, not rocket science. If any of this is unclear let me know. Thanks for all your input. My 753 appears to be a healthy unit. Sigh of relief. Graham.
 

Tazza

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Okay it is fixed and here is what I found out. I jacked up the rear a few inches and removed both rear wheels. Removed both side covers. marked the top pressure hose so as not to put them back on the wrong fittings. Removed all 3 hoses on each motor. Removed the 4 retaining bolts and slid out both motors. On the left side the seal on the carrier shaft looked just fine but I replaced it with the newer design. To do this I removed the seal and retainer with a screw-in seal puller. The seal looks like one piece but the seal is a seperate part. I used the old retainer part to press the new seal unit into place. The newer design is one piece. Need to be careful not to damage the seal as it is a very tight fit. On the right side I found the seal had fallen out of the retainer and was not even on the shaft. After re-installing the motors I ran the machine to pump out all the old oil, then re-filled with new oil. Then re-installed the 6 hoses to the motors with new o-rings. It appeared to have no leaks so I drove it around for 40 minutes the hydraulic oil level had not changed (allowing for heat expansion). That's it, not rocket science. If any of this is unclear let me know. Thanks for all your input. My 753 appears to be a healthy unit. Sigh of relief. Graham.
Glad to hear you got it all sorted out!
 
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