Where is the lift arm relief on the the valve body ?Anybody got pics would be great.. or suggestion on what could be the problem.. i can lift the the bucket up and let off the pedals and the bucket will slowly come back down. ANY HELP WOULD BE APPRECIATED.. THANKS CHRIS
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Is the valve relief one of the 1" caps on the end of the assy? BOBCAT DEALER HAS ALREADY REBUILT BOTH CYLINDERS.. NEED CONTROL VALVE HELP...
The port relief is the 1" valve next to the lift spool on the back of the valve and is a good bet that either the seals on it are bad or if this machine has the lift bypass valve next to the throttle lever it could be the problem as well?
IF I PLUG THE TWO LINES GOING TO THE BYPASS VALVE IT SHOULD TELL ME IF ITS THE PROBLEM RIGHT????? THANKS CHRIS
Yes.
tried plugging the manual relief lines and still same problem
I am still not sure what system you have, do you have a bics combo valve? meaning does your control valve have an black electric coil in the center of the tubelines? if so the next step would be to check the lock valve, make sure the seals on it are good. What is the best way to do pictures here? are they allowed?
i have seen some pics but not sure how to post them on here. i have now just went ahead and removed the control valve assy. from the machine. yes i believe this is the bics valve assy.. when you separate the assy. by removing the six bolts that holds it together there are four big ports with orings and one small port with an oring. one of the big ports holds the lift base end restrictor.. which hole is it ??? i think it fell from the bottom left hole with the bottom being as if the assy is on the machine..
As you have the control block out, all you can do is FULLY re-seal it, ensure you do the load checks as well, they will probably be the problem if the cylinders have been re-kitted and the relief is not damaged or leaking.
HOW DO YOU LOAD CHECK THE CONTROL VALVE??? ANY INSTRUCTIONS??
No, the "load checks" are PART of the control block. From what i hear, they prevent the arms from dropping when you move the spool to lift it some more, they are a spring and poppet that holds the high pressure in place. They also run seals that can and do go bad over time and can cause ram drift.
Tazza you are correct in the operation of the load checks, but they do not have seals and are in the circuit only when shifting the spool,they are a spring and poppet that holds the high pressure in place while pump pressure equilizes with lift circuit pressure. when in neutral they can not cause the lift cylinders to drift. I was referring to the pilot operated bics valves. they have four seals each and can cause the lift or tilt to drift depending on what valve is leaking. I ramble sometimes or so my wife tells me, I hope this made sense?
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The piston seals on one or both of your lift cylinders is leaking past, or it can be the control valve the foot pedal attaches too.
You can pressure test the seals on the cylinder piston with compressed air and see if they are sealed or bypassing the piston and escaping out the opposite port on the barrel.
If the pistons are sealing. then hook a 3000 psi pressure guage to the hose that goes to the back end of the cylinder and plug the hose going to the opposite side of the machine on the back end of that cylinder.
Start the machine and push the pedal to lift the boom. The guage pressure should rise (the boom should not lift if you hooked into the right hose and plugged the other one) to about 2250 to 2500 psi and stay near there when you release the pedal. If the pressure drops back down to 0 you have a problemwith a internal leak in the control valve or a bad hose. (the hose is unlikely because you would notice the oil leaking out everywhere)
Ken
Erosk - The load checks i re-did on my 743 machines all had seals on them, not sure if the later model control blocks have a different setup or not. The seals were not at the poppet and spring, they were on the body of the plug to seal i assume high pressure zones inside the castings of the the control block. There then was another O ring to seal the outside of the plug to the body. The other seals were O rings and backup rings.
When you separate the control valve by removing the six bolts there is a restrictor that goes in one of the holes ,, Does it go in with the legs down or up???The restrictor looks like a washer with four legs..
With the legs in the air, you want the restrictor to seat when the lift cylinder base end oil travels back into the valve and let the oil go around to the cylinder when lifting. Tazza do you have a gresen valve in your 743 or a melroe valve?
so if you are looking at the control valve with the bottom big hose facing you the restrictor goes in the bottom right hole with the flat side down into the hole??? is this correct
I think the large ports are aux. you want the bottom rear small port, item 49. trying a pic dont know if it will work.
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