Cat 416 Backhoe bucket curl suddenly got weak

[catgo22]

Digging out a stump and our 1989 Cat 416 Backhoe bucket curl function suddenly got weak. Rest of backhoe and loader functions seem normal. Backhoe bucket does curl but seems to have little force. No cylinders leaking, no hoses blown (a hose rupture is what I thought initially). Would that most likely be a seal in the backhoe valve group? Thanks.

 

[Billrog]

I thing a seal on the piston would do that.

 

[catgo22]

Bill. Thanks. Do you mean a seal on the spool inside valve group or the seal on the piston inside the curl cylinder? The curl cylinder piston seal makes sense. Easier to get to and rebuild first. Thanks.

 

[BukitCase]

Dunno much about Cat, but most hydraulic control valves are a "lapped to fit" between bore and spool - you're more likely to see a very GRADUAL change in one, where the cylinder itself can lose an O ring between strokes... Steve

 

[catgo22]

Thanks seemed like it happened quick. I'll get that cylinder rebuilt and update...

 

[crashz]

We had linkage issues with the actual stick. See if there is a rock or something binding the lever. If I remember correctly, our 416 had rod ends and cables that controlled the valves and a couple of the ends came off the cables.

 

[catgo22]

We had linkage issues with the actual stick. See if there is a rock or something binding the lever. If I remember correctly, our 416 had rod ends and cables that controlled the valves and a couple of the ends came off the cables.

Thx Crashz.. This old girl's valves are a little sticky but loosen up after it's run awhile. We did bang the levers a little just to see if we weren't getting full travel. And nothing was in the linkage causing a problem. Changed seals in the curl cylinder and now have replaced O-rings in the curl spool valve. Problem still there - it will curl bucket but has no strength in that function. All other functions are full strength. Mechanic noticed that when moving lever to curl in the dirt, if he also moved lever to bring stick in - curl suddenly got stronger. Seems like something in the valve group is crossleaking? Running up a big bill chasing it.

 

[catgo22]

Conclusion... Next option was replace entire valve group with used valve from Component Services Inc in Elwood Indiana. Wanted $1250 for the valve. A plug - super nice people and offered a couple of ideas on replacing pressure relief valves before changing whole valve group. Decided I'd had enuff. Know when to fold. Machine was 30 years old. Did not want to spend big money knowing age and other potential problems would be working against me. Bought a 15 year old, 3500 hour Deere 310SG and got $8K for old Cat as was. Done.