I have a late 90's 763 F series with the Bics or system. I' told it is the newer of those models. The machine has 800 hours on it but sat up for a while. I got it working and it sprung a spool valve leak. To repair the two spool valves, I lifted the boom in the air and used the orange lock out on the cylinder. I removed the hose that goes to the red lever and the pressure relief of regulator that is mounted facing closest to the front of the machine and linkage that connects the spool valve. I had a lot of trouble with stripped allen screws and spare time to do it that delayed the repair for several months. All hydraulics worked fine other than the spool valve leaking. Finally I completed the spool valve repair and assembled everything back to working order. Filled the machine with hydraulic fluid and changed the main hydraulic fluid filter in the engine compartment. The machine was running great so I got in to lower the boom. When I got in the machine as this is a new machine for me I forgot to engage the traction control button. I started pressing the pedals and couldn't get the boom or bucket to lift. It would move slightly but not enough to raise the bucket enough to remove the lift arm safety lock out to lower the boom. I noticed when the boom would slightly move up or down it would wiggle where the left arm (if your sitting in the cab your left) was trying to move but because the other side is locked out it couldnt. After trying to raise and lower it the seal on the left cylinder started spewing hydraulic fluid. I have now removed the arm and began the seal rebuild on the lift arm on the left side with the boom raised with the lock out in place on the right cylinder that is still on place. I finally did remember that I had to press the traction control button to make the hydraulics work. I engaged them and even with the leaking cylinder before I removed it, I could get the bucket to tilt full range both ways just fine. I never could get the boom to lit enough to tae out the lock out safety feature. I'm lost as to why that cylinder is almost acting as if its dead as even with the side that was leaking tried to move the boom would flex up or down with the other side not moving a bit ether way. I understand the other side is not going to lower because it is locked out and that is the purpose. I cannot figure out why it wouldn't raise at all? The only thing that happened during the long spool valve repair was that the pressure regulator or relief valve that bolts into the hydraulic control valve (same block the spool valves are in) had dropped in the grass. I cleaned it off no less than 20 times with cleaner. I'm not even sure what it does but is the only thing that I can think of. Its the regulator that faces the front of the machine next to the two spool valves towards the top of the control block not the one under that or the one under the spool valves. Any ideas what may cause this? I think it could be that pressure is being lost due to the leak but I think that it is wishful thinking. Im at a loss other wise?
Whaty would cause one boom lift cylinder to work and not the other?
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I loosened the steel tube connection on the cylinder at it had a good bit of fluid leaking out before I tightened it back down. I also watched the cylinder I just repaired extend out when I pressed the pedal to raise the boom so the rod could be put in place to reconnect to the boom. SO now I have no leaks as the leaking cylinder was repaired and the pedal moving freely. I had the left cylinder that was leaking raising and lowering ok without any leaks now while the right one has fluid because it was leaking out when I loosened the steel tube on the right side that has the safety lock. I just cannot get the boom to raise high enough to remove the lock off the right cylinder. I have no idea at this point. Fluid is full. Any more ideas anyone? Im lost on this one.
[FONT=Arial, Helvetica, sans-serif]I now have more strange issues. I kept stepping on the pedal and it just would not lift up any higher to get the safety lock out disengaged from locking out the lift cylinder. I kept using the tilt bucket pedal and then pressed the green switch to engage the aux hydraulics. When the green light indicated aux was on I flipped the switch on the handle to work them. As usually the noise it makes when you hit them came from under the seat and the lift arms began to move up raising the boom about 3 or 4 inches so I could now lift the safety lock out of the way. Now with the boom down I moved the machine to another spot in my yard. I could lower the boom pressing the left pedal to lower ( your left if you are sitting in the cab) and then when I would flip the switch for aux hydraulics it would engage and raise the boom all the way in the air. I could then lower back to the ground and do this over and over. I shut the machine down. I then started it back up a few minutes later and tried again. This time I could not raise the boom at all. When I hit the aux hydraulics this time it began to lift the bucket.[/FONT]
I'm not getting any leaks any place. The dealer said I may have a crack inside the control valve but I just don't see that. It was working ok when I parked it to replace the spool valve seals. I did not hammer or force anything. I pulled them out. I didn't take the caps off the spool valve stems to avoid those bb's popping out. I only replaced the o rings and put back in. I did not take the very top spool valve apart at all as everyone said leave it alone.
Any ideas?
A crack is possible, but i'd like to suspect sticky or damaged aux hydraulic stems. Working in that area, there is a rich of bumping them which can bend them. The best way is to get hold of a hose and connectors to loop the aux hydraulic connectors.
It's just weird that it lifts the arms when activated, it could be a crack, but i wouldn't be sure of that just yet.
I still have to try to loop the aux hydraulics and the stems but I'm just completely lost as to what is wrong. Tracking my hydraulic lines comparing to the diagram the dealer provided for my serial number, I found that my aux and my tilt lines were crossed although they did not actually cross so in order to put them like they are shown in the diagram I had to put one under the other and cross them to swap how they connect. I sis do on the rubber lines where they connect to the steel tubes on the boom as the rubber lines come out of the engine compartment. After I swapped them I cranked up the machine and gave it a try. Still have the same issue. The pedal on the left makes the boom barely raise but will let it come down as it was when the hoses were connected the other way. The boom will not raise from any pedal movement but when aux is engaged and I flip the switch on the lever it will raise the boom up if I flip the switch either way but then will not let it down. To let it down I have to either pull the red lever by the throttle or step on the pedal to lower as it should. Also, I think the bucker tilt is working backwards but I have to make sure of that. I have no idea what would happen if I hooked up something to the aux. Anyway after driving it around a little bit and working it on picking up some cement just to see what would happen she blew the tilt cylinder seal and shortly after blew the other lift arm seal. So now that I have rebuilt the other lift arm, I have to do the other lift arm and now the tilt cylinder. While I realize both seals were old and the thing has been setting up it seems like they are getting pressure build up and blowing the seals due to pressure.
Tazza, i'm going to try the methods you suggest before pulling the whole valve out of the machine but I'm getting close to throwing in the towel that it is a crack in the valve itself. I looked at the valve. Old machinist posted a pic of the valve on my machine in another thread. First if I get a length of hydraulic hose, where am I trying to run it from and too? On what ports and one I do this what am I trying to accomplish and would I need to run the aux or would it be automatic that I would be able to tell?
Also, to get the aux stems out. I'm a little lost on that. Where are they located and what is supposed to be taken off to get to them. Are they under the coils at the top of the valve or do you access them another way? Also, even if I do not have to take the coils (solenoids) off to get to the stems, If I ever have to change out the coils \, how do you remove them from the control valve block? Do they unscrew out of the block or is it removed by taking that nut off the top of the coil in the center?
Last but not least does anyone here know where I can get a used 763 control valve for a decent price? does anyone know who makes that control valve and the part number or where I would find it on the valve?
As an added note I know have had the hydraulic lines crossed and then crossed them the other way as mentioned in my second to last post above. Nothing changed so how can the lines going to the tilt cylinder and the aux hydraulics react the same way regardless if they are crossed or not?
The aux stems are indeed under the coils. Remove the nut on the top and slide the coils off. Then using a spanner, remove the stems from the control block.
Keep in mind that oil will start to flow out the holes, it's best to drain what oil you can before stating this.
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I'm almost inclined to think that perhaps when you reinstalled the valve assembly that one of the lines going to the aux hydros was crossed with one of the main boom lines... Have you checked where all the lines coming out of the valve are going?
I checked all of the lines and they did have the two lines going to and from the bucket and the two lines going to and from the aux swapped but bot to anything else. Another words the line going to the tip of the cylinder on the aux was connected to connection on the bottom and vice versa. I didn't have the aux attachments and another attachment crossed. Either way I swapped them and that was not it. I will be have time to tinker with it in the next day or two. I'm thinking next I will check stems under the solenoids and clean those up and if I get the same result I'm going to pull the spools again and go in there with a boroscope and see if I can find any cracks.
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