1991 743 no hydraulic functions

[huda9514]

this is my first post on here and I need help. the bobcat dealer has told me nothing and want way too much money to come out and service it. so I loaned it to my brother in law a year ago and he ran it for a while and said that the lift started to chatter and slow down but still drove fine forward and reverse. he changed the hyd oil and filter and it didn't change. so he parked it and I got it back and had the same problem. I ran it because I thought it was just air. I cracked a few lines and got some air out but had the same problem. I used it about a month ago and drive function worked perfectly but the lift and tilt still were slow and chattering. I used it for about 15 minutes then parked it to let any air work its way out. I shut the machine off and let it sit for about a week. here's where my problem got worse. I started it back up, it runs great, but now nothing worked. no lift no tilt and now no drive. also the red light that I assume means there is no oil pressure on the upper right hand side inside the cab is lit. which it wasn't before I turned it off. I looked on the internet at this site and many others for answers and one thing that I found was that it might be the vane pump and after checking all other things that would be less expensive I ordered a new vane pump. After replacing it there was no change. Hydraulics still have no function. also when I try to use any function there is no noise as to the pumps even sounding like they are trying to work. any help or info will be greatly appreciated, thank you in advance

 

[Bobcatdan]

The u joint good? Other then that, there is propper fill procedure when doing something like a vane pump so you don't fry the vane pump off the bat.

 

[billrbg]

Alas, I'm heading on a long road-trip in a few hours and won't be able to participate here much for a while. Do you have the hydraulic schematic handy? If not, look in the current thread started by "619atv". It sure sounds like the vane pump isn't functioning. I know, from blowing many hoses and draining the tank dry, that air purges out quickly by itself; that isn't likely to be the problem.

 

[Tazza]

Alas, I'm heading on a long road-trip in a few hours and won't be able to participate here much for a while. Do you have the hydraulic schematic handy? If not, look in the current thread started by "619atv". It sure sounds like the vane pump isn't functioning. I know, from blowing many hoses and draining the tank dry, that air purges out quickly by itself; that isn't likely to be the problem.

I'm thinking u-joint too. If nothing is working, it's a place to start.
If you remove the hydraulic pump (the front pump under the cab) you will see a shaft hanging out, if you turn the engine over and this doen't move, the connection between pump and motor is broken.

 

[7LBSSMALLIE]

I'm thinking u-joint too. If nothing is working, it's a place to start.
If you remove the hydraulic pump (the front pump under the cab) you will see a shaft hanging out, if you turn the engine over and this doen't move, the connection between pump and motor is broken.

quick check. drive and lift and tilt are separate. if both gone it b drive line coupler. . one shaft from eng turininig A lh drive b thru ainternal coupler rh drive C onto pump for lift and tilt. in syponis you will lose all hyd functions as in drive lift and tilt if coupletr sheared.

 

[huda9514]

So after a year of procrastinating I finally decided to tear back into the problem. I took the advice from an answer on here and removed the vane pump and turned the motor over and the shaft coming out of the drive pumps spun. this made me worry on I might not have gotten any further. just so happened a buddy asked me to take the vane pump shaft out and see if the splines are good on the other side. I did this and he took the shaft and said, " this is broken". I looked and I could plainly tell the shaft had sheared right off. I had not noticed it when I put the new vane pump on it because it was a clean break. I ordered it from bobcat and it was about $200. I do believe that the vane pump was going bad and that is what led to the shaft breaking. I installed it the other day and started it up and it worked! I have lift and drive functions again. if anyone has these same problems I did and needs the vane pump shaft the bobcat part number is 6512934 hope this helps someone in the future

 

[Tazza]

So after a year of procrastinating I finally decided to tear back into the problem. I took the advice from an answer on here and removed the vane pump and turned the motor over and the shaft coming out of the drive pumps spun. this made me worry on I might not have gotten any further. just so happened a buddy asked me to take the vane pump shaft out and see if the splines are good on the other side. I did this and he took the shaft and said, " this is broken". I looked and I could plainly tell the shaft had sheared right off. I had not noticed it when I put the new vane pump on it because it was a clean break. I ordered it from bobcat and it was about $200. I do believe that the vane pump was going bad and that is what led to the shaft breaking. I installed it the other day and started it up and it worked! I have lift and drive functions again. if anyone has these same problems I did and needs the vane pump shaft the bobcat part number is 6512934 hope this helps someone in the future

Glad you found the problem. There must have been just enough friction on the shaft for it to turn, even though it was broken.
If you knew, you should have called loader parts source to get another shaft, i'd like to think they would have charged less for that shaft. But as it's working now, it was money well spent.
If the vane pump locks up from wear or a broken vane, it will snap the shaft.