Hi Guys, I have a 763 which has the single ram in the center for operating the curl. There is no indication of leaks in the ram. When I have a weight on the bucket it will curl downwards on its own and not hold level. Just started doing it a couple of days ago. Hydraulic level is at proper level. Any idea what I should start checking to pinpoint the cause?
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7LBSSMALLIE
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there all sorts of tech troble shoot on this. easy brezzy repack cyl. kit 35 . get it outa way first. still leaks off we go deeper. but if you want the detailted t/s prouc for tilt drift glad to give it.
7LBSSMALLIE
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by the way what you are going to find is piston nut backed off.
It could be the nut backed off. I replaced the rod in the cylinder a couple of years ago and put new seals in at that time. Its possible I didn't get the nut tight enough though I do tend to over tighten things. I'm going to check the spool valve before I do anything. I suspect there might be a leak. If I do have to replace o-rings in the spool valve, do you know if I have to pull the whole valve out or is it possible to leave the valve in place and fix the leak?
Most like the cylinder. The control vavle itself is doubtful. Only way the vavle can do it if it's crack. The vavle itself is sealed by the oil itself. The seals in the vavle are wiper seals that keep the oil in. On the vavle there are port relief vavles. Small chance one is not seating and causing the problem. These were issues on older 40 series, but not so on the newer ones.
Thanks Dan. I really appreciate you taking the time to reply. I'll take the cylinder off and pull it apart and see what is going on.
7LBSSMALLIE
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keep us posted please as to what you find? also a little known fact is the piston retaining nut is critacial to keepining it tight examine youll stampinings on one side, this goes away from piston. should have a smidgen of lube on mate surface to be able to acheieve proper torque. S/B yada whatever. but it works. also keep in mind that no one acuattly uses a torqe wrench on these . its a 3/4 ratachet and five foot o pipe.
I will post an update on what I find. I pulled the cylinder off and have it laying on the bench but have not yet taken it apart. I also picked up a seal kit. Figured even if it's just the nut as long as I have it apart I'll put new seals in it. I won't get time to work on it until Friday. I can guarantee that I didn't put a pipe on it when I tightened the nut last time. I may have used an air ratchet and if not then I probably just tightened it with a wrench. Sounds like it needs to be really, really tight though!
SkidRoe
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A little bit of blue Loctite probably wouldn't hurt either. Hit the threads with some brake cleaner before applying. Cheers - SR
Remove both hyd. hoses from the cylinder & cap them off with steel caps / plugs, then cap / plug the fittings going to the cylinder. Raise the arms up, does the bucket still tilt downward on its own?? If so, the internal seals are bad / bypassing fluid. You can even put some dirt in the bucket to speed up the process.
I got the ram apart. The nut on the end of the rod was very loose so that was definitely a problem. I was going to just tighten the nut and put it back together since the seals were replaced a couple years ago but then I noticed that the seal on the piston was actually split in half (torn). Also a problem. I forgot that I had a service manual for it. According to the service manual, there is an o-ring that goes under a sort of tan colored seal on the piston. It said to remove o-ring, remove seal, install o-ring, then stretch the seal on a special tool until it would fit over the piston and slide down into the groove. Then you're supposed to install a ring compressor for 3 minutes to force the seal to compress back into its original shape. Well, I installed the small o-ring, then worked the seal over the piston and into the groove. I have to borrow my ring compressor back from my son in-law before I can put it back together though. Oh, and when I replaced the seals a few years ago I never put an o-ring under that tan seal on the piston. It has always worked fine though, surprisingly. Also, on the cap end I don't have an o-ring with a backer washer like most seem to have. Instead, I have a green seal that has two parallel ridges on the seal. Presumably it acts sort of like if you had two o-rings side by side. The only o-ring on the cap is the one that creates the seal near the threads and serves as sort of a gasket when you put it back together. So all in all I found 2 things wrong. Missing o-ring under the seal and a loose nut. I tightened the hell out of that loose nut and did use blue loctite on it.
I got the ram apart. The nut on the end of the rod was very loose so that was definitely a problem. I was going to just tighten the nut and put it back together since the seals were replaced a couple years ago but then I noticed that the seal on the piston was actually split in half (torn). Also a problem. I forgot that I had a service manual for it. According to the service manual, there is an o-ring that goes under a sort of tan colored seal on the piston. It said to remove seal, remove o-ring, install o-ring, then stretch the seal on a special tool until it would fit over the piston and slide down into the groove. Then you're supposed to install a ring compressor for 3 minutes to force the seal to compress back into its original shape. Well, I installed the small o-ring, then worked the seal over the piston and into the groove. I have to borrow my ring compressor back from my son in-law before I can put it back together though. Oh, and when I replaced the seals a few years ago I never put an o-ring under that tan seal on the piston. It has always worked fine though, surprisingly. Also, on the cap end I don't have an o-ring with a backer washer like most seem to have. Instead, I have a green seal that has two parallel ridges on the seal. Presumably it acts sort of like if you had two o-rings side by side. The only o-ring on the cap is the one that creates the seal near the threads and serves as sort of a gasket when you put it back together. So all in all I found 2 things wrong. Missing o-ring under the seal and a loose nut. I tightened the hell out of that loose nut and did use blue loctite on it.
7LBSSMALLIE
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you have done well my friend. couple notes on cyl repack. A. kit is genric may have more parts than you need. (but will have all the parts you need). it covers a half a dozen cyl's soleft over parts is not an issue.. now on to my personal experience with bobcat cyls. of all the brands ive dealt with this is by and far the easiesit. . unless you jack it over with a pipe wrench. or chain wrench. in which case your fucked.
Thanks. I got it all back together and its working great. I had been skeptical that the ring compressor would force that seal back to its original diameter but darned if it didn't! The seal looked great after 3 or 4 minutes in the ring compressor. I really want to thank everyone who helped. Its amazing that you guys knew the nut was probably loose and you were right! That's impressive. You saved me a lot of wasted time chasing my tail. So thank you all again! Most appreciated!
The difference in the seal kit versus what you took off is most likely due to newer revisions of the older parts. Very glad to hear that you got it right. I hope you tightened the $hit out of that flipping large but. Like another poster said, be sure to use a large 3/4" drive breaker bar with a long cheater pipe over the end for the very most torque possible. I've never installed the smaller o-ring under the nut or the piston because I've never seen an o-ring there to be replaced. I've generally had great results, nonetheless, tough. ROCK ON!!!
