1989 Bobcat Hydraulic drive issue

[Sgabino2]

I have a 1989 bobcat 743 that I use on my farm down in south Florida. I was working the machine the other day when I blew a hose that goes to the right side drive motor. The machine was going backwards when it blew, I was grading some dirt. I replaced that blown hose along with the two other hoses for that drive motor and one additional hose that I saw could use replacing. All hoses were connected back properly and the machine was topped off with hydraulic fluid.

The issue now is that when I attempt to start the machine the right side drive begins to turn in reverse, like the machine is stuck in reverse on that side. As the starter motor cranks the right side tires begin turning back. I looked over all linkage and can confirm it’s not a linkage issue. I inspected the shuttle valve on the right side drive and it appears to be clean and actuating. Not sure how this operates. Any assistance is much appreciated

 

[davedj1]

I know you said all hoses were connected properly but it sounds like you may have two of them in the wrong places. I don't know if that's possible or not but there should be a hose that returns to tank to let it freewheel. Is the control lever stuck/pushed on? I've seen that happen on a backhoe.

 

[Sgabino2]

Thanks for the reply. Ive looked over the hoses and they appear to be correct. When I had the new replacements made they were all specific sizes so can't really have them mixed up as far as location goes. The pump will create pressure as the motor cranks to where it walks the machine backwards on the right side as its trying to start. Even if I hold both lever forward while trying to start it will still act the same. I tried switching the two hoses on the right drive motor and the problem was the same except the machine would move forward on the right side. Since this issue no other hydraulic controls appear to function. It is almost as if all fluid is being directed through the right drive motor and not allowing other systems to work.

 

[oldnslo]

I just looked at Bobcat parts website and could not find a 743 that had three hoses going to the drive motor. All the diagrams showed two hoses to each drive motor.

What other hoses did you replace?

I know skid steers are difficult to work but any chance you could post some pictures of the hoses you replaced and what they connect to.

parts diagram also looked like the direction of travel linkage is all mechanically connected directly to the drive pumps is this correct?

 

[davedj1]

I did some searching and the "creep" seems to be an issue with that model/series too.
Does it need to be bled?

 

[Sgabino2]

Here are the pictures of the 3 hoses that were replaced going to the right side drive motor. The other hose is a large hose that runs through the back side of the machine from one side to the other and that can't have any other placement.

 

[dirttoys]

I have a 773, the only way I can think this would happen is stuck spool valve. I don't think you could mis route hoses to do this. Follow the linkage, examine the valve it controls.

Best,

ed

 

[oldnslo]

In the picture you posted and labeled you have the rear vane pump shown connecting to the drive motor this would definitely cause the problem you are experiencing. The two work ports on the hydrostatic drive pump should connect to the two work ports on the drive motor.

 

[Sgabino2]

Okay, I seem to be missing the issue. Could you describe to me what needs to be done to correct this ?

 

[oldnslo]

Attached is a copy of the hydrostatic circuit from Bobcat parts diagram. Not sure if correct serial number but this one had the vane pump shown and listed. I attempted too identify - list which hose number goes where in respect to the hydrostatic drive and vane pump on the rear of the hydrostatic pumps. Hopefully this picture is worth a 1000 words.