Bobcat 743 No Hydraulics Please Help

flhdisel · Jan 5, 2012

Hello All, First time posting to any forum, any help would greatly be appreciated. I have an old Bobcat 743 that I had a line blow on the left drive motor, I lost all fluid. There was no squealing, grinding or banging but the cat just slowed down to a stop, that's when I got out of the machine and noticed the leak. I replaced the line and filled the tank with Mobil 424 Hydraulic/ Trans Fluid but did not change filter. The Bobcat drove and lifted fine before the leak. Now when I start the Bobcat the red Transmission Warning Light stays on and I have no hydraulic functions at all, bucket or drive. I am sure there is a ton of air in the system because of running it empty and I had to remove other hoses to get to the one I replaced. I left the cap off of the hydraulic reservoir for 48hrs to see if any air would escape. The previous owner painted over the filler glass and unfortunately I overfilled the reservoir. I since then have removed the paint but that is not helping me right now. My questions are: 1. Is there a way to bleed the air from the system? 2. How can I tell if the hydraulic gear pump or motor is working? 3. Could the Mobil 424 oil that was recommended to me be way to thick? 4. Will it harm the pump running the machine at idle at a low rpm with the trans warning light is on (not driving but trying to move the bucket)? 5. Is there a relief valve somewhere that may be damaged? Please any help or troubleshooting steps would be appreciated. Sorry for the lengthy post but want to make sure I covered everything.

Tazza · Jan 8, 2012

How long was it running after the hose blew? Did you shut it off as soon as it happened?
Is there any noise when you try and lift or tilt? does it try and lift at all? or is there just nothing

flhdisel · Jan 8, 2012

Tazza said:
How long was it running after the hose blew? Did you shut it off as soon as it happened?
Is there any noise when you try and lift or tilt? does it try and lift at all? or is there just nothing

I was driving forward when the line blew. I did not know the line blew right away, the machine slowed down gradually and then came to a complete stop. I thought at first the fuel filter was clogged or some type of fuel issue. I then tried reverse which moved back about three or four feet or so until it stopped. I then began to raise the bucket, it moved up slowly so I dropped it right away. I then realized it must be a leak. I got out of the machine and saw the oil leaking out of the left drive side. I shut down the machine as soon as I saw the leak but by this time as I stated the machine already came to a stop, there was no banging, grinding or screeching. There is no noise at all when I try to lift or tilt, it does not even try, there is absolutely nothing . It is like the pump is not even turning on. It feels like there is no pressure at all. I also tried engaging the auxiliaries, still nothing, not even a sound. The transmission warning light remains on. However, when the line blew the transmission light did not come on, this is the first time that I have seen it. I'm lost, any trouble shooting guidance would be great. Thanks Tazza

lfutrell · Jan 8, 2012

flhdisel said:
I was driving forward when the line blew. I did not know the line blew right away, the machine slowed down gradually and then came to a complete stop. I thought at first the fuel filter was clogged or some type of fuel issue. I then tried reverse which moved back about three or four feet or so until it stopped. I then began to raise the bucket, it moved up slowly so I dropped it right away. I then realized it must be a leak. I got out of the machine and saw the oil leaking out of the left drive side. I shut down the machine as soon as I saw the leak but by this time as I stated the machine already came to a stop, there was no banging, grinding or screeching. There is no noise at all when I try to lift or tilt, it does not even try, there is absolutely nothing . It is like the pump is not even turning on. It feels like there is no pressure at all. I also tried engaging the auxiliaries, still nothing, not even a sound. The transmission warning light remains on. However, when the line blew the transmission light did not come on, this is the first time that I have seen it. I'm lost, any trouble shooting guidance would be great. Thanks Tazza

On my 743 I did a simple cyl rebuild, and after restarting it had broken a vane in the pump and locked it up and twisted the little drive shaft off that turns the pump. Just something to take a look at. these parts are available at loader parts source.

flhdisel · Jan 8, 2012

lfutrell said:
On my 743 I did a simple cyl rebuild, and after restarting it had broken a vane in the pump and locked it up and twisted the little drive shaft off that turns the pump. Just something to take a look at. these parts are available at loader parts source.

Thanks- I will take a look at both.