773 Aux Hyds

[Leequinn007]

Hi all, new to forum, just purchased 1999 773 Bobcat with 740 hrs showing. I am using a root rake with grapple on it. I can't get the grapple to hold hyd pressure on the arms while I tilt or lift the bucket. Is this normal? It's a PIA while trying to get stump on rake and not be able to hold pressure on grapple arms while rolling the rake back or lift. I hold the tilt foot peddle down and work the switch on handle to operate the arms. As long as I hold both functions nothing works. I can release one and the other works. I am hoping this is not normal function. Thanks

 

[Tazza]

To an extent it sounds normal from what i can understand of your issue. You can't run two functions at full power at the same time, but they will operate. Say you have a 4 in 1 bucket and grabbing on to a log, you hold the aux in place to keep grabbing at it, you won't have anywhere near full lift and tilt power, but you shouldn't need to keep the aux engaged to keep the log in the bucket jaws. It should grab and hold it there, the bucket shouldn't open when you lift or tilt the bucket.
With the grapple, is it holding the object even after you let go of the thumb switch? If not, it may be as simple as a bad piston seal in your grapple cylinder.

 

[Leequinn007]

To an extent it sounds normal from what i can understand of your issue. You can't run two functions at full power at the same time, but they will operate. Say you have a 4 in 1 bucket and grabbing on to a log, you hold the aux in place to keep grabbing at it, you won't have anywhere near full lift and tilt power, but you shouldn't need to keep the aux engaged to keep the log in the bucket jaws. It should grab and hold it there, the bucket shouldn't open when you lift or tilt the bucket.
With the grapple, is it holding the object even after you let go of the thumb switch? If not, it may be as simple as a bad piston seal in your grapple cylinder.

Thanks for the reply. When I clamp the grapple and release the switch the grapple will stay put. When I try to roll back or lift and activate a function with foot pedals, the instant the valve actuates the grapple will jump releasing some or all clamping. I would think once the travel of arms stop the Hyds should hold pressure but with no flow since arms have traveled as far as they can consuming no more flow. When I try to use the aux along with lift or tilt nothing happens until I release the aux switch. How can I use something like a hyd brush cutter if I can't raise or tilt as long as it is running? I want to think that all functions should work at same time although slower of course. Am I wrong in this thought?

 

[Tazza]

Thanks for the reply. When I clamp the grapple and release the switch the grapple will stay put. When I try to roll back or lift and activate a function with foot pedals, the instant the valve actuates the grapple will jump releasing some or all clamping. I would think once the travel of arms stop the Hyds should hold pressure but with no flow since arms have traveled as far as they can consuming no more flow. When I try to use the aux along with lift or tilt nothing happens until I release the aux switch. How can I use something like a hyd brush cutter if I can't raise or tilt as long as it is running? I want to think that all functions should work at same time although slower of course. Am I wrong in this thought?

That is an odd fault, when you grab and let go of the switch it should indeed stay clamped.
When operating multiple hydraulic components at once, the speed and power will be reduced, but they should all work unless one is bottomed out taking all the pressure. It also depends on what order it is in the valve body too (just to complicate things a little more). Essentially the function closest to where the oil comes in gets the highest priority, then it moves to the next and so on.
The brush cutter should still work as it's not under full load, when it's really bogging down, that's when you may have issues with lift and tilt.
I don't know why your aux is letting go when you lift, how well does your aux hydrailc control work on the bucket? do you have nice steady control in both directions? just wondering if something could be sticky.
Have you changed the main hydraulic filter too? as the aux hydraulic stems i believe use charge pressure to move the main spool.

 

[Leequinn007]

That is an odd fault, when you grab and let go of the switch it should indeed stay clamped.
When operating multiple hydraulic components at once, the speed and power will be reduced, but they should all work unless one is bottomed out taking all the pressure. It also depends on what order it is in the valve body too (just to complicate things a little more). Essentially the function closest to where the oil comes in gets the highest priority, then it moves to the next and so on.
The brush cutter should still work as it's not under full load, when it's really bogging down, that's when you may have issues with lift and tilt.
I don't know why your aux is letting go when you lift, how well does your aux hydrailc control work on the bucket? do you have nice steady control in both directions? just wondering if something could be sticky.
Have you changed the main hydraulic filter too? as the aux hydraulic stems i believe use charge pressure to move the main spool.

When I use the aux switch everything works as it should, good controllable speed and force. If I use the trigger on front of handle, constant flow, the grapple clamps and holds but no raise or tilt. When I clamp and then raise or tilt you can see just a bump to the arms, but sometimes with heavy load it's enough to let it get away. I just ordered a filter kit and will change fluids and filters when they arrive. This machine has set for the last few years and from the looks of it, it may have been used to push snow and slush from parking lot. The only other problem I have encountered, and it may be connected, is that the bucket leveling control is not functioning. I haven't had time to do anything except check fuses on this, they are all good. I use the Rotella 15w40 oil in my Diesel engines, do you see any problem using that for hydro fluid?

 

[Tazza]

When I use the aux switch everything works as it should, good controllable speed and force. If I use the trigger on front of handle, constant flow, the grapple clamps and holds but no raise or tilt. When I clamp and then raise or tilt you can see just a bump to the arms, but sometimes with heavy load it's enough to let it get away. I just ordered a filter kit and will change fluids and filters when they arrive. This machine has set for the last few years and from the looks of it, it may have been used to push snow and slush from parking lot. The only other problem I have encountered, and it may be connected, is that the bucket leveling control is not functioning. I haven't had time to do anything except check fuses on this, they are all good. I use the Rotella 15w40 oil in my Diesel engines, do you see any problem using that for hydro fluid?

If it has self leveling (bucket positioning), when you press the button on the dash, the light should come on, is it coming on and are you sure it's fitted?
As for the oil, i actually run engine oil in my hydraulics, but others refuse to do so as the engine oil does have additives that may not go well with the hydraulic system. Each to their own though on that.
Still not sure about your aux hydraulics not holding pressure though, seems very weird to me