S770 hydraulics not holding open grapple bucket

[Moonshadows]

New to the forum New machine (new to me) I just purchased a 2013 s770 2200 hrs seems to have been well taken care of everything works as it should except I have an issue with the hydraulics I mounted my grapple to it and grapple opens and closes perfect but once I open it it slowly closes by itself the cylinders on the grapple where just rebuilt the too and it grabs and holds tight so I don't think it's cylinder related. My grapple is a grapple rake type attachment so I open it all the way push into a pile of brush then close it onto the pile and away I go ——- what happens now is I open all the way and as I start toward the pile the top part starts to fall/close. It's as if there is a "float" type function engaged on the aux hydraulics allowing it to slowly close Anyone have any suggestions? Maybe a solenoid not closing? Maybe some fancy sett8ng I haven't figured out? (I did figure out how to make the hydraulics run constantly (do8ng that makes the grapple slam shut quickly) )

 

[Moonshadows]

I was hoping someone had something to add ——- I took my grapple to a friends house to verify if it would work on another machine and it works perfect on his machine My guess is the aux valve on my machine might not be fully seating? But if that where the case wouldn't it allow pressure out causing the grapple to forcefully open or close?

 

[Moonshadows]

I was hoping someone had something to add ——- I took my grapple to a friends house to verify if it would work on another machine and it works perfect on his machine My guess is the aux valve on my machine might not be fully seating? But if that where the case wouldn't it allow pressure out causing the grapple to forcefully open or close?

Is there any type of "float" function for the auxiliary hydraulics?

 

[Tazza]

Is there any type of "float" function for the auxiliary hydraulics?

My first idea was a bad cylinder, i'd like to think they were rebuilt correctly, but there is always a chance a seal was damaged...
Can upi cap pff one cylinder at a time to see if it still does it?
The aux circuit does not have a float position, it shoul dbe on or off, when off, it should hold the load on it.

 

[Moonshadows]

My first idea was a bad cylinder, i'd like to think they were rebuilt correctly, but there is always a chance a seal was damaged...
Can upi cap pff one cylinder at a time to see if it still does it?
The aux circuit does not have a float position, it shoul dbe on or off, when off, it should hold the load on it.

That would make the most sense!! However I pulled the grapple attachment off took it to my friends place and put it onto his s185 and it worked perfect rock solid up rock solid down didn't drift close, held firm. I'm not a hydraulic expert but I can usually figure out what's going on and I rebuild my own valves and cylinders on my old tractors but this issue has me baffled ——

 

[Tazza]

That would make the most sense!! However I pulled the grapple attachment off took it to my friends place and put it onto his s185 and it worked perfect rock solid up rock solid down didn't drift close, held firm. I'm not a hydraulic expert but I can usually figure out what's going on and I rebuild my own valves and cylinders on my old tractors but this issue has me baffled ——

Ok, so that proves that the issue is not the attachment, I wonder if your aux hydraulics are not centering just right. But surely that would make the grapple slowly open or close on it's own when running.
The control block will have 2 springs, one at each end of the spool, if one was broken, it would not center properly, but again, that would mean any attachment would still operate on it's own....

 

[Moonshadows]

Ok, so that proves that the issue is not the attachment, I wonder if your aux hydraulics are not centering just right. But surely that would make the grapple slowly open or close on it's own when running.
The control block will have 2 springs, one at each end of the spool, if one was broken, it would not center properly, but again, that would mean any attachment would still operate on it's own....

That's what I thought! It doesn't make sense!!!

 

[foton]

That's what I thought! It doesn't make sense!!!

maybe the spool is galled and bypassing slightly in one direction. boy is that a guess.

 

[Moonshadows]

maybe the spool is galled and bypassing slightly in one direction. boy is that a guess.

One thing for certain I'm going to have to tear into it one of these days to figure it out. I originally posted hoping someone would say "oh that's a common problem, here's how to fix it" —— I guess that didn't workout

 

[creelinecat]

One thing for certain I'm going to have to tear into it one of these days to figure it out. I originally posted hoping someone would say "oh that's a common problem, here's how to fix it" —— I guess that didn't workout

check the auxillary couplers on the boom of the machine, ive changed a bunch of those, once they have an internal leak they cant hold the pressure any more

 

[Moonshadows]

check the auxillary couplers on the boom of the machine, ive changed a bunch of those, once they have an internal leak they cant hold the pressure any more

Thanks for the tip I'll look into it

 

[franklee95]

Not sure if this was ever solved but the quick connects have releases that bleeds pressure when pushed in to a case drain so bad quick connects on the machine will cause this issue