753c aux hydraulic question

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DAWGFAN

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Apr 19, 2006
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i just bought a 753c with 1500 hrs on it good clean tight machine however i am using a 72 inch bobcat grapple bucket on it and when i release the grapples on the bucket the right one will leak down the left one stays up also when i have the grapples clamped i dont seem to have enough pressure to move the bucket up or down or to tilt it any info would be much appreciated. the controls are on the right hand lever a thumb lever and a trigger for constant on and off thanks again for any help
 

Tazza

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How are you keeping the graples shut? if there is a bad seal, you will have to hold pressure to it, this will cause your relief valve to open causing loss of pressure to your other hydraulics. From what you are saying, i would suspect your seals on the cylinder that falls down are broken.
 

DAWGFAN

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How are you keeping the graples shut? if there is a bad seal, you will have to hold pressure to it, this will cause your relief valve to open causing loss of pressure to your other hydraulics. From what you are saying, i would suspect your seals on the cylinder that falls down are broken.
I WOULD SAY THAT WOULD BE TRUE THE CASE TO BUT MY BROTHER INLAW USES THIS SAME GRAPLE ON HIS 873 AND THE CYLINDERS STAY UP IM CURIOUS IF IT HAS SOMETHING TO DO WITH THE PUMP BECAUSE IT IS THE CYLINDER THATS FURTHEST AWAY THANKS FOR THE REPLY
 

Tazza

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I WOULD SAY THAT WOULD BE TRUE THE CASE TO BUT MY BROTHER INLAW USES THIS SAME GRAPLE ON HIS 873 AND THE CYLINDERS STAY UP IM CURIOUS IF IT HAS SOMETHING TO DO WITH THE PUMP BECAUSE IT IS THE CYLINDER THATS FURTHEST AWAY THANKS FOR THE REPLY
Well you have me there....
As for the distance, that will not be an issue, the pump pressurises the fluid evenly, no matter how far away, it should still work the same, the distance between the 2 are all of 6 feet at most.
Is your fluid foamy at all? thats the only other thing i can think of.... If it is foamy, it will not pressurise the fluid properly, it will get hot quicker and will make groaning noises. Check your fluid level to be sure.
Other than that, i have no idea what it could be... Sorry
 

DAWGFAN

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I WOULD SAY THAT WOULD BE TRUE THE CASE TO BUT MY BROTHER INLAW USES THIS SAME GRAPLE ON HIS 873 AND THE CYLINDERS STAY UP IM CURIOUS IF IT HAS SOMETHING TO DO WITH THE PUMP BECAUSE IT IS THE CYLINDER THATS FURTHEST AWAY THANKS FOR THE REPLY
ok guys got home today checked the aux again i even swaped the fittings same thing happens the right hand grapple goes down i got out of the cab and i can push both grapples down i push on one and the other will raise up. if i push the aux button to make both green lights come on and hit the trigger switch to lower the grapples into the bucket and keep constant pressure on them then i cant raise or lower the arms of the loader nor can i raise or lower the bucket till i press the trigger switch again i say i cant it will move a little but very slowly as in slooooow thanks again for any input
 

Tazza

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ok guys got home today checked the aux again i even swaped the fittings same thing happens the right hand grapple goes down i got out of the cab and i can push both grapples down i push on one and the other will raise up. if i push the aux button to make both green lights come on and hit the trigger switch to lower the grapples into the bucket and keep constant pressure on them then i cant raise or lower the arms of the loader nor can i raise or lower the bucket till i press the trigger switch again i say i cant it will move a little but very slowly as in slooooow thanks again for any input
That will be your problem, *if* i understand you correctly, you are using your aux. hydraulics to apply pressure to the grapple rite? now when its down you should NOT lock your aux hydraulics on, just use it to open or close. When you have grabed the item or closed the grapple take your thumb off the lever and it will stay put as the hydraulic oil will hold it there under pressure. If you hold it down, the oil will just be going over the relief vavle and you will get VERY slow or no movement on your lift and tilt.
I hope i understood you correctly with what you discribed.
As for when you move one arm and the other cylinder goes the other way, that is eaxctly what it should do.
 

DAWGFAN

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Apr 19, 2006
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That will be your problem, *if* i understand you correctly, you are using your aux. hydraulics to apply pressure to the grapple rite? now when its down you should NOT lock your aux hydraulics on, just use it to open or close. When you have grabed the item or closed the grapple take your thumb off the lever and it will stay put as the hydraulic oil will hold it there under pressure. If you hold it down, the oil will just be going over the relief vavle and you will get VERY slow or no movement on your lift and tilt.
I hope i understood you correctly with what you discribed.
As for when you move one arm and the other cylinder goes the other way, that is eaxctly what it should do.
sorry i have a hard time explaining things, but yes if i have steady pressure on the grapple this is when the lift or the bucket will not work properley. problem is that if i grab something (say a small stump to pull out of a brush pile and the grapple doesent shut all the way) i will end up loosing the object because the hydraulics are not holding the grapple down unless i keep the thumb switch on or the finger trigger locked. after releasing the switches i loose pressure thanks again
 

skidsteer.ca

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Dawg Your rh grapple arm is leaking down because the cylinder on that side is shot. It need new internal seals to prevent oil from bypassing from one side of the piston to the other. This is also the reason you can't hang onto objects. Your should have only one green aux hyd light on when using attachments with cylinders. And you use the RH side thumb switch to open or close the cylinder(s). If you close it and it loses pressure that is most likely a bypassing cylinder. Two green aux hyd lights and the finger trigger is for running attachments that need continous flow like a brush cutter motor,or a backhoe attachment. If used to run a cylinder the actions you describe are normal. By the way how do you open the grapple? Go back to using the thumb switch? Anyway, rebuild your rh cylinder, use the thumb switch and you'll be in business. The cylinder must have gone south since you got it from your brother? if it did not leak shut on his machine. I replied to your other post with a description of how to test the cylinder. regards Ken
 

DAWGFAN

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Apr 19, 2006
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Dawg Your rh grapple arm is leaking down because the cylinder on that side is shot. It need new internal seals to prevent oil from bypassing from one side of the piston to the other. This is also the reason you can't hang onto objects. Your should have only one green aux hyd light on when using attachments with cylinders. And you use the RH side thumb switch to open or close the cylinder(s). If you close it and it loses pressure that is most likely a bypassing cylinder. Two green aux hyd lights and the finger trigger is for running attachments that need continous flow like a brush cutter motor,or a backhoe attachment. If used to run a cylinder the actions you describe are normal. By the way how do you open the grapple? Go back to using the thumb switch? Anyway, rebuild your rh cylinder, use the thumb switch and you'll be in business. The cylinder must have gone south since you got it from your brother? if it did not leak shut on his machine. I replied to your other post with a description of how to test the cylinder. regards Ken
i undone the hydraulic lines on the bucket yesterday while i had the grapples up and just my luck they are still up in the air this morning, so at least i know its in the loader now. the only reason i was using the trigger was to grab something and hang on to it without having to use my thumb all day. hopefully when i get the loader fixed i want have this problem anymore got a guy coming monday to look at it. he worked for bobcat for @10 yrs he works on heavy equipment know so i believe he can help me out with the loader. i'll let you guys know thanks for all the input
 
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