Bobcat 331 Excavator Arm Cylinder Inoperative

[dgerard]

Hello, I blew a seal in the arm cylinder of my 1998 Bobcat 331 mini excavator. After having the cylinder rebuilt, everything worked fine until the cylinder suddenly quit working. No movement forward or back. Everything else works fine. Any suggestions on what could be causing the problem and how to fix it?

 

[flyerdan]

If I were to venture a guess, I'd suspect that the piston came off of the rod, and the fluid is just going through the center mounting hole and out the other port.
That would be most likely if the cylinder was mid-travel, and there wasn't an obvious sound of it going into bypass due to an obstruction at one of the ports.
If that is the case, fixing it should be just taking it apart, dumping out all of the loose parts, putting it back together with loctite or safety wire, depending on style. If you had a shop do it, they should sheepishly do all this for you at no cost.

 

[dgerard]

If I were to venture a guess, I'd suspect that the piston came off of the rod, and the fluid is just going through the center mounting hole and out the other port.
That would be most likely if the cylinder was mid-travel, and there wasn't an obvious sound of it going into bypass due to an obstruction at one of the ports.
If that is the case, fixing it should be just taking it apart, dumping out all of the loose parts, putting it back together with loctite or safety wire, depending on style. If you had a shop do it, they should sheepishly do all this for you at no cost.

Are you referring to the spool valve?

 

[bobbie-g]

Are you referring to the spool valve?

From my limited experience, I'm pretty sure he's referring to the hydraulic cylinder itself. The large actuating rod will have a piston or disc attached to it inside the cylinder, most likely held on by a nut threaded on to the end of the rod. If the disc comes loose (if the nut was not secured well to the end of the rod with safety wire or loctite), it would no longer make the rod move in and out. Let us know how this works out. ---Bobbie-G

 

[dgerard]

From my limited experience, I'm pretty sure he's referring to the hydraulic cylinder itself. The large actuating rod will have a piston or disc attached to it inside the cylinder, most likely held on by a nut threaded on to the end of the rod. If the disc comes loose (if the nut was not secured well to the end of the rod with safety wire or loctite), it would no longer make the rod move in and out. Let us know how this works out. ---Bobbie-G

When I disconnected the hose from the rear fitting and manually compressed the cylinder, fluid was forced out of the port. This leads me to think the problem isn't related to the cylinder itself, but the control circuit.