S750 tilt cylinder

[de03x7]

I work in a DOD maintenance shop and we had a 2011 S750 with 615 hours come in with the tilt cylinders not holding pressure. We found the nut loose on both tilt cylinders and the seal off of one stuck inside the hydraulic control valve body. The nut on both tilt cylinder rods were loose and the piston could move around 1 1/2 inches. The rods on both cylinders are bent where they made contact with the pivot boss on the Bobtach. Just something to watch out for. I don't know if this is a widespread problem but it will save you a lot of downtime and money if you catch it before damage is done. A quick check would be to pull the lower pin on the tilt cylinder and see if there is any play in the rod.

 

[Bobcatdan]

This was a known issue on M series. Normally when the settling problem was noticed, the nut was hardly loose and not really backed off at all. I'm guessing your guys ran it a long time with the settling issue, my guess to the point where the bucket dropped so bad they couldn't use it. I'm on the fence whether that caused your rods to get bent or not. If they are in theory a 1/2" longer, possible that could be enough to allow them to over extended to the point of being bent. Or your guys are just hard on equipment.

 

[de03x7]

This was a known issue on M series. Normally when the settling problem was noticed, the nut was hardly loose and not really backed off at all. I'm guessing your guys ran it a long time with the settling issue, my guess to the point where the bucket dropped so bad they couldn't use it. I'm on the fence whether that caused your rods to get bent or not. If they are in theory a 1/2" longer, possible that could be enough to allow them to over extended to the point of being bent. Or your guys are just hard on equipment.

The operators are young soldiers who will bust an anvil if given the chance so that is the first issue. I posted pictures of it on the Bobcat facebook page but you can see where the rod was making contact with the pivot pin boss on the bobtach and that is right where the bend is at. The nut had backed off to where there were only a couple threads keeping it on the shaft. The piston moved an inch and a half or more and it allowed enough movement that the seal came off and a section of it was jammed up in the control valve. Yes the bucket dropped so bad it was unusable. My guess is that they were using it for hard pack and it over extended to the point of bending. We have sent out the call for them to bring the other 5 or 6 machines they have to us so we can check them before the get this bad.

 

[Tazza]

The operators are young soldiers who will bust an anvil if given the chance so that is the first issue. I posted pictures of it on the Bobcat facebook page but you can see where the rod was making contact with the pivot pin boss on the bobtach and that is right where the bend is at. The nut had backed off to where there were only a couple threads keeping it on the shaft. The piston moved an inch and a half or more and it allowed enough movement that the seal came off and a section of it was jammed up in the control valve. Yes the bucket dropped so bad it was unusable. My guess is that they were using it for hard pack and it over extended to the point of bending. We have sent out the call for them to bring the other 5 or 6 machines they have to us so we can check them before the get this bad.

That's pretty bad form from Bobcat, i thought the manual said to use red loctite on the nuts to prevent this happening, i wonder why they didn't do that in the factory?
Sadly nuts to back off from time to time, i have only had one machine that this happened to, every other one was tight, tight enough to require a bar to get the nut off.
I'm with Dan, over extension, no matter how small can cause rods to bend.
I wouldn't blame the operators for the bending, if they weren't over extended, they wouldn't be able to bend.

 

[Bobcatdan]

That's pretty bad form from Bobcat, i thought the manual said to use red loctite on the nuts to prevent this happening, i wonder why they didn't do that in the factory?
Sadly nuts to back off from time to time, i have only had one machine that this happened to, every other one was tight, tight enough to require a bar to get the nut off.
I'm with Dan, over extension, no matter how small can cause rods to bend.
I wouldn't blame the operators for the bending, if they weren't over extended, they wouldn't be able to bend.

The issue was mainly with a bad batch of cylinders where the nuts were not propperly torqued. It was a relatively common event for a period of time then pretty much went back to normal after we repaired most of the effect machines. After I left, I know they were having issues with track drive motors not being propperly torqued and leaking. It was so bad, the replacements had the same problem.

 

[de03x7]

That's pretty bad form from Bobcat, i thought the manual said to use red loctite on the nuts to prevent this happening, i wonder why they didn't do that in the factory?
Sadly nuts to back off from time to time, i have only had one machine that this happened to, every other one was tight, tight enough to require a bar to get the nut off.
I'm with Dan, over extension, no matter how small can cause rods to bend.
I wouldn't blame the operators for the bending, if they weren't over extended, they wouldn't be able to bend.

I agree it's tough to lay this on the operator. Maybe if they were more experienced they would have noticed it sooner but when you are shown this is where the key goes, these handles make things work and you are now an operator this is what you expect. We plan to have the rest of the ones here brought in so we can check them before it comes to bent rods and seals going through the system. We will go ahead and pull them apart if there is any indication of looseness. It would have been nice if Bobcat had put out a warning to watch for this and maybe they did through their dealers. Being that these are owned by DOD any recall notices would not necessarily get to the users.