Spool stuck in valve body.

[Babongo]

My Bobcat 642 malfunctioned. While operating, the lift arms uncontrollably rose to full extension. The tilt cylinder also extended fully. Both foot controls felt jammed and were unresponsive. At the hydraulic control valve, we noticed that the top spool was protruding more than normal. At the rear, the end cover of this spool had cracked, and one mounting ear was separated from the cover. We disconnected the linkage, and attempted to remove the spool from the rear. We removed the end cap (pieces), and attempted to slide the spool out the rear. It slid about 1 inch, then stopped. It sounded and felt like metal to metal interference. We removed the load check nut, which was intact, and seemed fine. Same result. The spool is stuck. It does rotate freely. Can anyone offer some insight? Are we missing something, should anything else be removed to release the spool? This is a 3 spool control valve, Bobcat #6586287.

 

[laurencen]

take a look at the parts diagrams on Bobcat site if you do not have a manual, there my be a detent ball on the end that has moved, can you rotate the spool?

this will get you to find a breakdown of valve Bobcat Genuine Parts Catalog – Official Bobcat Company site

 

[Babongo]

Laurencen, I do have the diagram you attached, thank you. All 4 ball bearings were accounted for, the springs were mangled. The spool does in fact rotate freely, a good question on your part, where an inability to rotate would suggest a bent spool. I am having a hard time imagining the sudden release of the spring pressure at the angle created by the cracking of one end cap ear would be enough to chip any internals....

 

[laurencen]

from my experience a bent spool will not fully rotate and hangs up, it is also not uncommon that the spool will move back and forth some but be tight coming out, what age is the machine?

over many years I have seen small O ring pieces prevent a valve moving, it could also stop the spool coming out if its between the grooves and port openings, why did the housing break? my best recommendation is take the valve out and carefully remove the spools to see what is going on, its not common for the spools to over travel enough to break the housing.

the other idea if the valve over traveled and the spring or washer dropped in the spool grooves the cast housing could have a burr formed and this will also prevent removal, easily seen on the bench

 

[Babongo]

This skid steer is over 30 years old. One end cap screw probably started to loosen, stressing the flange. I've found out that Melroe/Bobcat redesigned the end caps with more robust flanges.