new guy with 753 f aux hydraulic problem

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DAWGFAN

Member
Joined
Apr 19, 2006
Messages
8
sorry guys i posted this first in the wrong place i just bought a 753 f good machine however i am running a 72 inch bobcat grapple on it when i raise the grapples up the right one will leak back down rather quickly the left one stays up also when the grapples are shut i dont seem the have enough pressure to raise the bucket or to tilt it any info would be appreciated
 

skidsteer.ca

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Jan 20, 2006
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First of a 72" grapple is on the large side for a 753, but you may have also hit the nail on the head. Get a pressure guage and hook it into your quick couplers and see where you hyd pressure is at. If its up to spec, (my guess @ 2500 psi, but you would need to check that), you may be just trying to lift to much. As for your grapple closing on it own, I'd bet the hyd cylinder on the right side, needs repacked and is bypassing the piston internally. The test, unhook the hoses, push the rod in and out to remove most of the oil. Plug the port on the barrel end of the cylinder, and take the pin out of the rod end, hook your air compressor to the port on the rod end and pressurize it. If the packings are good the rod will retract into the cylinder and STAY there. If the cylinder is bypassing, the rod will retract then begin to extend itself. If you are trying too close the grapple and lift (or tilt) at the same time, this would definitely account for your lack of lifting power. See if it improves when you quit trying to close the grapple. regards Ken
 

DAWGFAN

Member
Joined
Apr 19, 2006
Messages
8
First of a 72" grapple is on the large side for a 753, but you may have also hit the nail on the head. Get a pressure guage and hook it into your quick couplers and see where you hyd pressure is at. If its up to spec, (my guess @ 2500 psi, but you would need to check that), you may be just trying to lift to much. As for your grapple closing on it own, I'd bet the hyd cylinder on the right side, needs repacked and is bypassing the piston internally. The test, unhook the hoses, push the rod in and out to remove most of the oil. Plug the port on the barrel end of the cylinder, and take the pin out of the rod end, hook your air compressor to the port on the rod end and pressurize it. If the packings are good the rod will retract into the cylinder and STAY there. If the cylinder is bypassing, the rod will retract then begin to extend itself. If you are trying too close the grapple and lift (or tilt) at the same time, this would definitely account for your lack of lifting power. See if it improves when you quit trying to close the grapple. regards Ken
i ended up posting this twice in the skid steer forum and here, ive been talking with tazza on it however this is my question when the grapple is up should there be enough pressure on the lines to hold it in position. once the right grapple leaks down half way i can push the left grapple down by hand and the right one will come back up if i grab something with the grapple (push the thumb lever and release it) and try to back up should there be enough pressure to hold on to the object without locking the auxs in almost seems like i might have a back flow problem thanks for the reply
 

DAWGFAN

Member
Joined
Apr 19, 2006
Messages
8
i ended up posting this twice in the skid steer forum and here, ive been talking with tazza on it however this is my question when the grapple is up should there be enough pressure on the lines to hold it in position. once the right grapple leaks down half way i can push the left grapple down by hand and the right one will come back up if i grab something with the grapple (push the thumb lever and release it) and try to back up should there be enough pressure to hold on to the object without locking the auxs in almost seems like i might have a back flow problem thanks for the reply
i have a hard time explaining things, but i only have a broblem with the lift and tilt if there is pressure on the grapples either up or down i can clamp over a log and pick it up fine when i just close the grapples but if grab the log with the grapple teeth to move it, it will slip out if i dont hold the thumb swithch or lock the auxs maybe there supposed to be this way but the leaking down is driving me nuts thanks again for any replys
 

Tazza

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i have a hard time explaining things, but i only have a broblem with the lift and tilt if there is pressure on the grapples either up or down i can clamp over a log and pick it up fine when i just close the grapples but if grab the log with the grapple teeth to move it, it will slip out if i dont hold the thumb swithch or lock the auxs maybe there supposed to be this way but the leaking down is driving me nuts thanks again for any replys
I understand you now. I still think its a problem with a leaky seal in the ram. If not, it will be a problem with a load check in your control block for the aux hydraulics. The load checks hold the high pressure oil in place when you release the control. The older spools had this, i'm un-sure if the late model ones still have this or not. Whn i had this problem, the arms would VERY slowly fall back to the ground, so it seems very un-likley.
Try un-coupling the quick disconnects with the grapples up in the air. They will be a little hard as there will be oil under pressure behind it. With it dosconnected see if it falls back to the ground. If it does, its definatly a ram piston seal and if not, its a problem with your loaders aux hydraulic spool.
Let us know how it goes.
 
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