bobcat 743 drive motor question

[richfrazier]

Hello everyone and thanx for a great forum to fall back on.I just got a bobcat 743 and its got a hydraulic leak. I was thinking it would be just a hose but its coming from one of the hydrostatic drive motors. On each of the motors, on the front side of the motors, are small holes about 1/8". On the dry motor the hole is plugged. The other motor is not plugged and the oil pisses right out of it. Is this a pressure relief valve? does it just need to be plugged back up? Any help would be great and thanks in advance!!

 

[SkidRoe]

It sounds like you have lost a blanking plug out of a cross drilling. Usually these are plugged with a ball bearing, and metal staked to hold it in place.
If that is the problem, find a bearing ball that fits snugly in the hole, drive it in if you have to, and then place center punch marks around the hole to stake it in place.
HTH - SR

 

[Tazza]

It sounds like you have lost a blanking plug out of a cross drilling. Usually these are plugged with a ball bearing, and metal staked to hold it in place.
If that is the problem, find a bearing ball that fits snugly in the hole, drive it in if you have to, and then place center punch marks around the hole to stake it in place.
HTH - SR

There are no cross drilled holes that are plugged off on these motors..... I'm wondering if these holes are the ones that are used to mount a model number to the motor. Are they about 1” apart on the large mounting part of the motor?
I'm wondering if there is a crack or something.

 

[richfrazier]

There are no cross drilled holes that are plugged off on these motors..... I'm wondering if these holes are the ones that are used to mount a model number to the motor. Are they about 1” apart on the large mounting part of the motor?
I'm wondering if there is a crack or something.

http://s1194.photobucket.com/user/joewhite400joewhite400/media/bobcat_zpspsytfxqg.jpg.htmlhttp://s1194.photobucket.com/user/joewhite400joewhite400/media/bobcat%203_zpsftop7hrc.jpg.htmlhttp://s1194.photobucket.com/user/joewhite400joewhite400/media/bobcat4_zpsikv8of90.jpg.html pulled the motor today and snapped a couple pictures...I hope they upload.

 

[richfrazier]

http://s1194.photobucket.com/user/joewhite400joewhite400/media/bobcat_zpspsytfxqg.jpg.htmlhttp://s1194.photobucket.com/user/joewhite400joewhite400/media/bobcat%203_zpsftop7hrc.jpg.htmlhttp://s1194.photobucket.com/user/joewhite400joewhite400/media/bobcat4_zpsikv8of90.jpg.html pulled the motor today and snapped a couple pictures...I hope they upload.

 

[billrbg]

Are you sure that is a (wheel) drive motor? Something doesn't look right to me; it and the ports to it look too small. I admit I have never seen my drive motors, but am pretty familiar with the hoses to them, some of the biggest on the 743.

 

[richfrazier]

Are you sure that is a (wheel) drive motor? Something doesn't look right to me; it and the ports to it look too small. I admit I have never seen my drive motors, but am pretty familiar with the hoses to them, some of the biggest on the 743.

I think skidroe might be right. I pulled the motor and cleaned it up to get a better look. It looked to be a part of the "case drain & reservoir system". So for a test I threw a temporary plug in the hole and put the motor back into the machine. I ran it for a hour with no leaks. So now I need to pull the motor out and do a more permanent repair and pray for the best. Does anyone know where I can find a manual for free on the interweb or am I just gonna have to buy one? I have the service manual but its not much help...I think im gonna need the parts manual.

 

[Tazza]

I think skidroe might be right. I pulled the motor and cleaned it up to get a better look. It looked to be a part of the "case drain & reservoir system". So for a test I threw a temporary plug in the hole and put the motor back into the machine. I ran it for a hour with no leaks. So now I need to pull the motor out and do a more permanent repair and pray for the best. Does anyone know where I can find a manual for free on the interweb or am I just gonna have to buy one? I have the service manual but its not much help...I think im gonna need the parts manual.

Must be a different version of motor, that is not a standard 743 motor.
Is it a 743B that you have?

 

[richfrazier]

Must be a different version of motor, that is not a standard 743 motor.
Is it a 743B that you have?

Honestly I don't know much about the machine. I was told it was a 1993 743. It looks like it was repainted awhile back and stickers removed. Ill have to double check the numbers next chance I get.

 

[SkidRoe]

Honestly I don't know much about the machine. I was told it was a 1993 743. It looks like it was repainted awhile back and stickers removed. Ill have to double check the numbers next chance I get.

That is most definitely a cross drilling, missing its ball bearing plug. You can see the mating hole in the back with its plug in place. But I have to say those connecting ports do look small... Can you post a picture of the entire machine?

 

[richfrazier]

That is most definitely a cross drilling, missing its ball bearing plug. You can see the mating hole in the back with its plug in place. But I have to say those connecting ports do look small... Can you post a picture of the entire machine?

Is there a reason for the plug coming out of the cross drilling? Could it be a internal seal gone bad and pressure shot it out or is it just that the plug/ball bearing let go?

 

[richfrazier]

Is there a reason for the plug coming out of the cross drilling? Could it be a internal seal gone bad and pressure shot it out or is it just that the plug/ball bearing let go?

Looking at the machine I think its a 743b. The number plate is missing but someone wrote 743b on the inside of the engine compartment. Whats the difference between the 743 and the 743b? It has the aux. hydro on the arms upfront if that's the difference.

 

[SkidRoe]

Looking at the machine I think its a 743b. The number plate is missing but someone wrote 743b on the inside of the engine compartment. Whats the difference between the 743 and the 743b? It has the aux. hydro on the arms upfront if that's the difference.

Most likely corrosion and/or a poor staking job lead to the ball letting go.
Differences between a 743 and 743B are quite minor (I think). I too would be interested in hearing an explanation. Aux location on the boom would not be a differentiator. This was standard on all 743 models.
Cheers - SR

 

[richfrazier]

Most likely corrosion and/or a poor staking job lead to the ball letting go.
Differences between a 743 and 743B are quite minor (I think). I too would be interested in hearing an explanation. Aux location on the boom would not be a differentiator. This was standard on all 743 models.
Cheers - SR

thanx to everyone that responded...you have been a huge help !!!

 

[Tazza]

thanx to everyone that responded...you have been a huge help !!!

If it's indeed 1993, it is not a standard 743, possibly the B version.
Does the key switch shut the engine off? are there bolts on the end of the axle hubs? and can you get a picture of where the motor mounts to the chain case?
As for the hole, can you tap/install a plug to stop the oil leaking out?

 

[SkidRoe]

If it's indeed 1993, it is not a standard 743, possibly the B version.
Does the key switch shut the engine off? are there bolts on the end of the axle hubs? and can you get a picture of where the motor mounts to the chain case?
As for the hole, can you tap/install a plug to stop the oil leaking out?

Ah, yes, bolt on hubs. I forgot about that one.
Be careful if you thread the hole for a plug. You don't want any of the metal chips to find their way into the motor. Also, coat the plug in a decent pipe sealant like Loctite 592, or similar, to ensure there are no leaks.

 

[richfrazier]

Ah, yes, bolt on hubs. I forgot about that one.
Be careful if you thread the hole for a plug. You don't want any of the metal chips to find their way into the motor. Also, coat the plug in a decent pipe sealant like Loctite 592, or similar, to ensure there are no leaks.

The key switch does shut off the engine. If I remember correctly there is one large bolt head in the center of the hub. Ill try to get a picture before I bolt the motor back on. I actually just finished drilling and tapping it. I installed the bolt with Loctite and a copper crush washer. I was able to push air through from the other side so I hope all the metal chips flowed back out of the drill hole. ill keep you posted !

 

[SkidRoe]

The key switch does shut off the engine. If I remember correctly there is one large bolt head in the center of the hub. Ill try to get a picture before I bolt the motor back on. I actually just finished drilling and tapping it. I installed the bolt with Loctite and a copper crush washer. I was able to push air through from the other side so I hope all the metal chips flowed back out of the drill hole. ill keep you posted !

Yup, that is a 743B. Bolt on hubs are a dead give away. Also, older 743's used a pull cable fuel shut off. All coming back to me now... : )

 

[richfrazier]

Yup, that is a 743B. Bolt on hubs are a dead give away. Also, older 743's used a pull cable fuel shut off. All coming back to me now... : )

I bolted the drive motor back in last night. It ran for about a hour and no leaks yet!! Ill post a picture of the repair as soon as I can(im not a smart phone user). What are you guys running for hydro oil?