Bobcat 763 arms creep up when attachments are used

[33fastr]

I have a problem that I could use your help with. The arms lift on their own when the bucket is tilted up or an attachment is being used. Thanks for any help you might be able to send my way.

 

[Tazza]

Could you be pushing your foot on the lift pedal slightly at all? if the spring that holds the spool in centre is broken or stretched some how, it could be out of centre and allowing them to rise.
The one you don't want to hear is thers could possibly be a crack in the control block allowing oil from the other functions to the lift cylinders.

 

[33fastr]

Could you be pushing your foot on the lift pedal slightly at all? if the spring that holds the spool in centre is broken or stretched some how, it could be out of centre and allowing them to rise.
The one you don't want to hear is thers could possibly be a crack in the control block allowing oil from the other functions to the lift cylinders.

Thanks for your quick response. I should also add that the arms raise only when the bucket tilt is all the way up or all the way down or an attachment (post auger) is attached. It works fine otherwise. Do you still think the spring is the culprit? Your knowledge is greatly appreciated.

 

[jlmoon]

Thanks for your quick response. I should also add that the arms raise only when the bucket tilt is all the way up or all the way down or an attachment (post auger) is attached. It works fine otherwise. Do you still think the spring is the culprit? Your knowledge is greatly appreciated.

I might be overloading myself here.. don't know the 763 very well!, but didn't some models have a self / auto leveling feature (don't know the principle of operation, but obviously a hydraulic function) which changes the tilt angle of the bucket as you raise up to keep level.. say for dumping dirt in truck etc. Could this hydraulic circuitry be causing pressure feed back into the boom cylinder hydraulic circuits? Just pondering a little! JLM

 

[jlmoon]

I might be overloading myself here.. don't know the 763 very well!, but didn't some models have a self / auto leveling feature (don't know the principle of operation, but obviously a hydraulic function) which changes the tilt angle of the bucket as you raise up to keep level.. say for dumping dirt in truck etc. Could this hydraulic circuitry be causing pressure feed back into the boom cylinder hydraulic circuits? Just pondering a little! JLM

to finish my pondering, Something has to be pushing fluid into the cylinder end of those boom cylinders and taking fluid from the rod ends of the same! Shared Equalizer / Balance valve block? don't know!

 

[Tazza]

to finish my pondering, Something has to be pushing fluid into the cylinder end of those boom cylinders and taking fluid from the rod ends of the same! Shared Equalizer / Balance valve block? don't know!

Bucket positioning isn't a bad idea actually, it diverts a percentage of the fluid going to the lift cylinders to the tilt cylinder to keep the bucket flat through the lift. It doesn't fully explain why it does it with something on the aux lines too....
If it was a crack, it would be more noticed when you reach the limit of a cylinder as pressure builds up more oil gets pushed through it.

 

[33fastr]

Bucket positioning isn't a bad idea actually, it diverts a percentage of the fluid going to the lift cylinders to the tilt cylinder to keep the bucket flat through the lift. It doesn't fully explain why it does it with something on the aux lines too....
If it was a crack, it would be more noticed when you reach the limit of a cylinder as pressure builds up more oil gets pushed through it.

I ordered a spring and seals and o-rings today. They should be in tomorrow. I'll keep you posted. There is no sign of any oil leaking. How can you tell if it's a bucket leveling problem? Thanks,

 

[Tazza]

I ordered a spring and seals and o-rings today. They should be in tomorrow. I'll keep you posted. There is no sign of any oil leaking. How can you tell if it's a bucket leveling problem? Thanks,

It would leak internally, so no oil woild be seen. Not all machines have this fitted anyway. It is a block that sits under the cab that tubes from the lift and tilt circuit go into straight from the control block. Sorry, i don't have a picture to help identify if you have one or not.

 

[lfutrell]

It would leak internally, so no oil woild be seen. Not all machines have this fitted anyway. It is a block that sits under the cab that tubes from the lift and tilt circuit go into straight from the control block. Sorry, i don't have a picture to help identify if you have one or not.

I have sort of the same problem, I have a log splitter with a open center valve so I can control it from the ground, when I bottom the cyl. out it will bypass like it should but the arms will raise about 1/4 inch, after a few pieces of wood I just let it back down. All this started after I rebuilt a leaking control valve

 

[[email protected]]

I have sort of the same problem, I have a log splitter with a open center valve so I can control it from the ground, when I bottom the cyl. out it will bypass like it should but the arms will raise about 1/4 inch, after a few pieces of wood I just let it back down. All this started after I rebuilt a leaking control valve

sounds like something isn't seated properly

 

[7LBSSMALLIE]

sounds like something isn't seated properly

check base and rod aux spool orings, try tilt back over relief if rises bics lock out valve orings try tilt out over relief if rises check port /anti cav. valve mind you this is top of head the stuff, further diagonatics were about 5 buds ago