Brand new CB65 backoe problem- UPDATE

[plowhog]

Got excellent dealer service to repair a bad seal in the backhoe ram. As explained in an earlier post, even with the engine running the backhoe would slowly drop.

Once a new seal was installed, all was well. But, after a few hours of digging, the problem returned. Another call to the dealer. The factory asked that I warm things up well, then extend the backhoe and turn the engine off. They wanted me to measure how many inches the ram extended (bled down) after ten minutes with the engine off. The measurement was easy. It had bled off the full extension of the ram after only 5 minutes.

I reported this back to the dealer. Fortunately, the hoe is useable although its a little annoying that it moves on its own. I'm waiting on word back, but the guess was that they might want to replace the entire ram. I'm not a mechanic, but I'm wondering if there is something internal that is scoring the seals and causing them to leak.

 

[thclimer]

Sorry to learn that the leak has returned and hope the dealer is able to fix it soon.

 

[TSO]

Sounds like they are at least trying to go the extra mile to get it squared away. Let us know...

 

[ray66v]

My wild guess is, it was made out of tolerance.

 

[hazmat ranger]

Just a thought: bad control valve?
A very good thread I read a while back ( I believe it was HEF) made a good point.
The cylinder rod, moving into or out of the cylinder, changes the volume of the cylinder. Fluid, being virtually incompressible, would prevent rod from moving (I likened it to putting your finger over a syringe and trying to move the plunger).
The point they made in the thread was that bad seal shouldn't cause cylinder drift...

Hope you get your hoe fixed soon.

DB

 

[ray66v]

The point they made in the thread was that bad seal shouldn't cause cylinder drift...

Sorry, that's incorrect.

There are two half's to a double acting cylinder.

If the seal between the two, does not hold, the fluid can leak from one side to the other.

The side that has the weight, or force on it, will have higher pressure, which can leak to the lower pressure side.

That is called an internal leak. And, that's what causes the drift down. Few machines don't experience it to some extent.

I've fixed plenty of cylinders, that had this problem.

Yes, there are other things, like check valves, and external leaks, that can cause this too.

I would expect, they will be replacing the cylinder.

 

[hazmat ranger]

Sorry, that's incorrect. There are two half's to a double acting cylinder. If the seal between the two, does not hold, the fluid can leak from one side to the other. The side that has the weight, or force on it, will have higher pressure, which can leak to the lower pressure side. That is called an internal leak. And, that's what causes the drift down. Few machines don't experience it to some extent. I've fixed plenty of cylinders, that had this problem. Yes, there are other things, like check valves, and external leaks, that can cause this too. I would expect, they will be replacing the cylinder.

Yes, that could be the cause. But, read the thread: Understanding hydraulics and cylinder drift The point I took away is: if you took the cylinder filled with oil, plugged the hose ports, then tried to force the rod in or out (with bad seals or even without a piston on the end), the rod is physically changing the volume of the cylinder (and acting on the fluid).
I can understand the difference between theory and field and that there may be other variables involved.

I hope it's an easy fix and he's up and running soon. DB

 

[AxleHub]

Plowhog,

As I recall you just got your unit recently. Did you notice this issue from the get-go?

Seems if it drops all the way in 5 minutes that its worse than before the seal was replaced.

Its nice to have a good dealer and warranty at times like this . . its even better if the 5 year warranty was still "new in box" amd shiny at the end of the 5 years

Fingers crossed it gets better soon

 

[plowhog]

I did not notice it at first. But I am a total greenhorn around a tractor so that doesn't mean much.

As best as I know, I am pretty sure it developed after I used the backhoe for a while. I noticed it dropping after having done digging for a while, and noticed that it seemed out of place. So, I do think I would have noticed it earlier had it been there when I first started digging.

Once the seal was replaced, the hoe did not move or drop at all. Zero. I'm pretty sure this means that the new seal fixed things, and then something internal caused that new seal to also go bad. The wild card is the fluid temperature. When the seal was replaced, the temps were only on the low side as I ran the tractor only long enough to test it. Since all seemed OK I didn't go any further. In hindsight, it would have been better to immediately dig with it and get all the fluids to normal operating temperature. That would have been a better test, and as it turns out, it might have revealed the problem again on the spot instead of waiting for the next tractor use.

 

[AxleHub]

I did not notice it at first. But I am a total greenhorn around a tractor so that doesn't mean much.

As best as I know, I am pretty sure it developed after I used the backhoe for a while. I noticed it dropping after having done digging for a while, and noticed that it seemed out of place. So, I do think I would have noticed it earlier had it been there when I first started digging.

Once the seal was replaced, the hoe did not move or drop at all. Zero. I'm pretty sure this means that the new seal fixed things, and then something internal caused that new seal to also go bad. The wild card is the fluid temperature. When the seal was replaced, the temps were only on the low side as I ran the tractor only long enough to test it. Since all seemed OK I didn't go any further. In hindsight, it would have been better to immediately dig with it and get all the fluids to normal operating temperature. That would have been a better test, and as it turns out, it might have revealed the problem again on the spot instead of waiting for the next tractor use.

Plowhog,

I've just a little less than a year of actual "tractor" experience. My past use of skidsteers and trenchers only applied a lityle to tractors. What I've learned in the last 10 months is . . operate safely and expect to always be learning. I don't think you did anything improper . . but now you've learned to double check repairs to see if they actually got repaired lol.

Keep the paint shiny . . its still a new tractor that just showed it wasn't quite weened away from the dealer yet . . it needs one last visit and then its ready to rip without getting homesick lol.

Its going to get better soon.

P. S. This spring I'll take mine in for its 50 hour (probably actually about 85 hour). Rojo (spanish for red) has a couple little things that need adjustment at the same time too.

 

[Fiziksgeek]

Someone correct me if I am wrong, but if you extended the boom then disconnected the hydraulic lines and it still bled down, wouldn't that tell you for for sure if its an internal leak on the cylinder?

 

[ray66v]

Yes.

But, I am not sure if you could disconnect the lines, with pressure in them.

 

[Billrog]

Since it held with the new seal for a short time I would guess there's a good chance they could have damage an O ring or the back up ring or piston seal when replacing which can be a bear to install properly.

 

[brettskermetzger]

Hey plowhog,

Just recently purchased a gc1720 and am noticing a similar issue with my backhoe...did you ever get this figured out?

 

[frugalangler]

Someone correct me if I am wrong, but if you extended the boom then disconnected the hydraulic lines and it still bled down, wouldn't that tell you for for sure if its an internal leak on the cylinder?

I'm not a hydraulics expert, but on the CB65 if you detach the lines from the tractor, the valve is still in the circuit as it's part of the hoe, and the QC is between the hoe and valve, and the tractor.
I'm curious also, because mine also sags if I leave it extended, but then again I was under the impression ALL hydraulics sag, hence never trust a hydraulic (anything) and always put a mechanical safety device (jack-stand, prop rod, etc.) in place to prevent injury due to sag. Mine only has 38 hours and every cylinder will sag under weight, 3PH, BH dipper and bucket and stabilizers, FEL lift and curl, all will over time. When I detach my BH, I put a stack of lumber under the frame because the stabilizers will sag, and the main arm will rise and I'll return to a BH frame flat on the ground. It jumps right back up when I attach hydraulics, but I just don't want it sitting on the wet ground if not necessary.

 

[jeepcj7]

A couple points. First, you can never have a zero leak valve, the valve spool always has to be a little smaller than the valve bore or the valve spool will never move when you try to move the valve lever/handle. 2nd - you need to determine where the leak comes from, the cylinder or the valve. It is very common for a cylinder to leak internally. To check for an internal cylinder leak, you need to either fully extend or retract the cylinder, remove the hose from the rod end of the cylinder if the cylinder is extended or from the barrel end of the cylinder if the cylinder is retracted. Wipe off any oil where the hose was removed, start the tractor and apply hydraulic pressure to side of the cylinder that is still connected to the hose. If a trickle of oil comes out of the cylinder where the hose was removed then the issue is the cylinder is leaking internally. DO NOT apply hydraulic pressure to the side of the cylinder where the hose was disconnected or you will spray oil all over the place.

 

[plowhog]

My cylinder apparently had a minor flaw. When a new seal was installed it would work for a short time, but a burr or something on the cylinder itself would re-corrupt the seal. A replacement cylinder fixed it.

If I park the tractor with the backhoe off the ground, it will slowly bleed down overnight until the bucket is on the ground. That is normal. But seeing it visibly dropping while the tractor was running was not normal. Again, a new cylinder fixed everything ...

 

[irvingj]

Thank you for the update!