630 turning problem

[dirtpig538]

I have a 630 Bobcat. Hydraulics on loader all work ok , but turning is a problem. It will turn a little bit either way, then doesn't want to turn any more. The oil seems to have water in it, it is white. Will this be at least part of the problem? What is the best way to remove the oil to replace?

 

[Tazza]

Lift the cab, on the hydraulic pump there is a block with three hoses on the left. Remove the middle hose and fitting, there should be a bronze filter. Remove, clean or replace it.
Hopefully yours is the same setup, this filter catches a lot of people.
Is the oil white after sitting? or only when it's been run? if it's only after being used, it will be air not water. If water, drain all you can by running the machine at idle and pump it out the aux couplers. When it starts to spit shut down. Re-fill with oil, drive it around, lift and tilt to move the oil, dump it again. Repeat till the oil is clean.

 

[dirtpig538]

Lift the cab, on the hydraulic pump there is a block with three hoses on the left. Remove the middle hose and fitting, there should be a bronze filter. Remove, clean or replace it.
Hopefully yours is the same setup, this filter catches a lot of people.
Is the oil white after sitting? or only when it's been run? if it's only after being used, it will be air not water. If water, drain all you can by running the machine at idle and pump it out the aux couplers. When it starts to spit shut down. Re-fill with oil, drive it around, lift and tilt to move the oil, dump it again. Repeat till the oil is clean.

I have cleaned the bronze filter a couple of times. Also, did what you said about replacing the oil. It may be just air. Still having the same problem with steering. Can you explain the pumps to me? Is there 2 hydrostatic pumps and also a hydraulic pump, and what is the function of each? What would happen if the hydraulic pump was weak or malfunctioning? Also, I have read about some replenishing valves. What if they are not working correctly? I just don't know where to go from here.

 

[Tazza]

I have cleaned the bronze filter a couple of times. Also, did what you said about replacing the oil. It may be just air. Still having the same problem with steering. Can you explain the pumps to me? Is there 2 hydrostatic pumps and also a hydraulic pump, and what is the function of each? What would happen if the hydraulic pump was weak or malfunctioning? Also, I have read about some replenishing valves. What if they are not working correctly? I just don't know where to go from here.

You are right, there are three pumps all joined together. The rear section is for the left, the next one is for the right side drive, the front pump is the hydraulic pump for lift/tilt/aux. It also works as the charge pump for the drive pumps.
I guess it is always possible that the pump is worn causing slow drive performance. If you cap the hoses from the motors and slowly push the steering levers forward and backwards, see how far it bogs the engine down. You should feel the sticks fighting you.
If the pump is worn, you can generally repair the wear with glass and sheets of wet and dry sand paper. You will need to crack the pump open to see if it is indeed worn or not though.

 

[dirtpig538]

You are right, there are three pumps all joined together. The rear section is for the left, the next one is for the right side drive, the front pump is the hydraulic pump for lift/tilt/aux. It also works as the charge pump for the drive pumps.
I guess it is always possible that the pump is worn causing slow drive performance. If you cap the hoses from the motors and slowly push the steering levers forward and backwards, see how far it bogs the engine down. You should feel the sticks fighting you.
If the pump is worn, you can generally repair the wear with glass and sheets of wet and dry sand paper. You will need to crack the pump open to see if it is indeed worn or not though.

So if the pump is worn, can I tell by checking the pressure at the sending unit port? What should the pressure be?

 

[dirtpig538]

So if the pump is worn, can I tell by checking the pressure at the sending unit port? What should the pressure be?

Checked the pressure on the vane pump. It is only at 60#. Should I replace the pump? Or could there be something else causing the low pressure?

 

[Tazza]

Checked the pressure on the vane pump. It is only at 60#. Should I replace the pump? Or could there be something else causing the low pressure?

You can dead head the drive pump hoses to see what the engine does. You can anlso install a gauge, it should get to 5,000 PSI

 

[Tazza]

You can dead head the drive pump hoses to see what the engine does. You can anlso install a gauge, it should get to 5,000 PSI

Sorry, i hit send far too early, i must be having one of those rush mornings.
How did you check pressure from the pump? did you T into the line? if so, dead head one of your rams, see what the pressure gets up to. Never dead head the hydraulic line from the pump without it first going through a relief valve. Something will let go.
Does the lift and tilt work properly? with such a low pressure, i'd have thought pretty much nothing would be working.
I'd start by removing the pump and checking that the shaft is not broken that links the drive pumps to the hydraulic vane pump.
If it's not broken, take the sections out and inspect for wear, keep the vanes in the rotar the same direction. They will be worn, you want them to go back in the same place.

 

[dirtpig538]

Sorry, i hit send far too early, i must be having one of those rush mornings.
How did you check pressure from the pump? did you T into the line? if so, dead head one of your rams, see what the pressure gets up to. Never dead head the hydraulic line from the pump without it first going through a relief valve. Something will let go.
Does the lift and tilt work properly? with such a low pressure, i'd have thought pretty much nothing would be working.
I'd start by removing the pump and checking that the shaft is not broken that links the drive pumps to the hydraulic vane pump.
If it's not broken, take the sections out and inspect for wear, keep the vanes in the rotar the same direction. They will be worn, you want them to go back in the same place.

What I did was put a gauge in place of the hydraulic pressure sending unit on the front of the port block. I have the pump apart. I can't see anything that looks like it is worn. The shaft is ok. The hydraulics seem to work ok, maybe a little weak under a full load, but it does lift and tilt. I can make it spin the tires in loose dirt, but not on solid sod. Also, it will turn on solid ground, but has difficulty on loose dirt.

 

[Tazza]

What I did was put a gauge in place of the hydraulic pressure sending unit on the front of the port block. I have the pump apart. I can't see anything that looks like it is worn. The shaft is ok. The hydraulics seem to work ok, maybe a little weak under a full load, but it does lift and tilt. I can make it spin the tires in loose dirt, but not on solid sod. Also, it will turn on solid ground, but has difficulty on loose dirt.

Ah, the charge pressure port is 90-120 psi, not full pump pressure.
I'd suspect the main drive pump is worn or the motor seals are leaking. Put the vane pump back together and in.
When you can't turn, does the engine pull down? if not, plug the hoses to the drive motors and slowly push the steering lever forward, see if it pulls the engine down. Just do it slowly, not a sudden push. You should be able to kill or almost kill the engine by doing this, if it bogs down, but not a lot, it is a pump wear issue.
If the pump is at fault, parts aren't too expensive. Some times you can repair the wear with glass and wet and dry sand paper.

 

[dirtpig538]

Ah, the charge pressure port is 90-120 psi, not full pump pressure.
I'd suspect the main drive pump is worn or the motor seals are leaking. Put the vane pump back together and in.
When you can't turn, does the engine pull down? if not, plug the hoses to the drive motors and slowly push the steering lever forward, see if it pulls the engine down. Just do it slowly, not a sudden push. You should be able to kill or almost kill the engine by doing this, if it bogs down, but not a lot, it is a pump wear issue.
If the pump is at fault, parts aren't too expensive. Some times you can repair the wear with glass and wet and dry sand paper.

Ok, so if my charge pressure is only 60, do you think that is enough? I don't want to put it all back together if you think that might be part of the problem.

 

[Tazza]

Ok, so if my charge pressure is only 60, do you think that is enough? I don't want to put it all back together if you think that might be part of the problem.

It is low, but i can't remember the correct value for your model machine. The pump does not directally generate the charge pressure, it is created on the fluid that goes back to the tank through the oil cooler.
The correct way to check the hydraulic pressure is at the aux coupler, this will tell you if the pump is generating pressure. As you said the arms do lift, it's working well enough to check the drive pumps.