Max 28 backhoe question

[DavesTractor]

On the tractor is should leak down but if its leaking down while disconnected id be checking for leaks... mainly at the hose connections... unless there is air in the system there is really no were for fluid to return to. Are you having to add Hyd fluid to the tractor often?

It can go to the other side of the cylinder past the piston seals with no external leaks. Only so much of that can happen without a leak if gravity is pushing the rod back into the cylinder (like having the stabilizers holding up the backhoe with it disconnected) as the rod displaces some oil. As you mentioned, the oil must go somewhere. That will sometimes cause the quick connects to be nearly impossible to re-connect as those hoses end up dealing with the extra oil and take on some pressure.

 

[Navasot]

It can go to the other side of the cylinder past the piston seals with no external leaks. Only so much of that can happen without a leak if gravity is pushing the rod back into the cylinder (like having the stabilizers holding up the backhoe with it disconnected) as the rod displaces some oil. As you mentioned, the oil must go somewhere. That will sometimes cause the quick connects to be nearly impossible to re-connect as those hoses end up dealing with the extra oil and take on some pressure.

Correct... I had one do this not to long ago and rebuilt the cylinders.. had to keep the old parts and show the customer for him to believe me ha. He keeps it on blocks now adays

 

[DavesTractor]

Correct... I had one do this not to long ago and rebuilt the cylinders.. had to keep the old parts and show the customer for him to believe me ha. He keeps it on blocks now adays

But let's not cause folks to think that if it settles it needs rebuilt. Settling is normal and expected. Actual specs for allowable settling are alarmingly high. Meaning it can settle a bunch and be within specs of a new cylinder.

 

[John Dougherty]

j wilson,
I apologize for the delay in getting back to you, I've been on vacation. The short answer is no. I haven't attempted it yet as I am waiting for the cap/plug that covers the bottom of the positioner that keeps the dirt out. It (cap) didn't come with the positioner assembly for some reason. Curiously, Dave's Tractor told me that the company that makes these caps had never had a request for a cap/plug in the past six years. While I believe them, all I can say is that the snap ring that secures the guts of the positioner was not properly installed. If that snap ring comes loose, then the parts will fall/blow out of the positioner housing. The 'housing' reminds me of a spark plug wrench for a chainsaw minus the screw driver handle. Obviously, the cap would hit the dirt and be lost. I have the new positioner and it looks pretty straight forward replacing the original one albeit a bit awkward because it's in the back row. Maybe JJ or Dave's can chime in on this process. Good luck, wish I could have been more helpful.

 

[Navasot]

But let's not cause folks to think that if it settles it needs rebuilt. Settling is normal and expected. Actual specs for allowable settling are alarmingly high. Meaning it can settle a bunch and be within specs of a new cylinder.

But in only a nights time? I let this one sit out disconnected after we rebuilt it for two days without any noticeable sag

 

[DavesTractor]

But in only a nights time? I let this one sit out disconnected after we rebuilt it for two days without any noticeable sag

Let me give you the specs for a JD backhoe, because we can all agree that JD is quality and they have been doing this backhoe thing for a while. A model 47 stabilizer cylinder is allowed 0.3 inch (8mm) per minute as measured at the rod. Under that and JD will tell you that your backhoe is fine. 0.3" as measured at the rod is a bunch, a patient man could sit there and watch it settle at that rate. That is per minute, not per hour. The main boom cylinder is allowed 0.6"/minute on that same JD.

If it were my backhoe and was near the max specs, I'd not be happy. That seems like too much leak-by travel. But you can be sure that a loader that is left 2 feet in the air at night and is on the ground in the morning might well be in specs. Even if left over lunch it might be in specs. These piston rings are lubricated by oil, there needs to be a little bit of leakage to make them last.

But you alluded to an important point. Why do some loaders left in the air stay there for weeks? I haven't a clue....

I'm no hydraulic expert, there is my disclaimer.

 

[John Dougherty]

Dave,
You do have one thing in your favor....you are a pretty nice/helpful guy.

 

[DavesTractor]

Dave,
You do have one thing in your favor....you are a pretty nice/helpful guy.

That is my make believe internet persona. It goes down hill from there.

 

[John Dougherty]

That is my make believe internet persona. It goes down hill from there.

Probably correct, but you fake it pretty well my friend!

 

[Navasot]

Let me give you the specs for a JD backhoe, because we can all agree that JD is quality and they have been doing this backhoe thing for a while. A model 47 stabilizer cylinder is allowed 0.3 inch (8mm) per minute as measured at the rod. Under that and JD will tell you that your backhoe is fine. 0.3" as measured at the rod is a bunch, a patient man could sit there and watch it settle at that rate. That is per minute, not per hour. The main boom cylinder is allowed 0.6"/minute on that same JD.

If it were my backhoe and was near the max specs, I'd not be happy. That seems like too much leak-by travel. But you can be sure that a loader that is left 2 feet in the air at night and is on the ground in the morning might well be in specs. Even if left over lunch it might be in specs. These piston rings are lubricated by oil, there needs to be a little bit of leakage to make them last.

But you alluded to an important point. Why do some loaders left in the air stay there for weeks? I haven't a clue....

I'm no hydraulic expert, there is my disclaimer.

:thumbsup: