312CL Issues

[wolf44]

OK here is how it started. The stick went crazy and went to full extension out on it's own and shut the machine down. Disconnected the lines from the cylinder and looped them back to the tank and moved it back to the shop.
Tried to pull the valve control rod controlling the stick out of the valve housing it was locked in place. after much screwing around finally got it out and found a mangled piece of metal about the size of a pea locking the valve shaft in the main valve body. then we drained the hydraulic tank and pulled all screens and the filters. Found 4 more pea size chunks' in the bottom of the screen. filters look good not any small fine grit in it at all, so far just 5 pea sized chunks. It looks like the stick cylinder has been replaced some time in the past. (clue- maybe ? ) This machine is new to me in the last 3 months. So far I cant see any place these chunks could have come from. Maybe when the cylinder broke last line and they did not get all the crud flushed out and it finally got loose and we have found the problem??
Here is my current plan lap the valve bore where the control rod moves freely again, pull the stick cylinder and take apart and look for more chunks in the cylinder , clean and flush all line and stick back together and see what happens.
Looking for any other suggestions on courses of action, kind flying by the seat of my pants on this one.
One more question any idea what the clearence should be between the valve shaft and housing bore?

Thanks for reading and any help you can give me.

 

[backhoe1]

I had something real similar happen on my deere, sounds like you're going at it the same way. just make sure to flush lines both ways from valve bank (I had some stick in a 90 that didn't get flushed because I only went one way).

 

[willie59]

I think you have the right idea tearing the stick cyl apart, that's probably where the debris came from. I don't know what the valve bore/spool tollerance is, but be careful working in that bore, if you change the diameter excessively, it will affect operation of that valve section. You might want to talk to a machinest, ask them what the best tool to work with to repair the bore.

 

[wolf44]

The valve shaft is(22.00 mm) .8660 at the top and it is .8657 at the bottom I ordered a .8670 reamer thinking that .001 clearance for a shaft 10.00 long would be tight but ok. Wrong! Dang thing was to tight to even go in. going to pick up a 22mm reamer in the morning and try again. What I have not done is tri-mic the bore but I will do this this afternoon.
I think I will make and expanding arbor to polish the effected area of the bore after getting the reamer to hand twist thru. I have already made a specical vac line attachment to clean up all the land areas, and remove all grit with right angle swabs that fit in the bore. ps that's what I do I own a CNC machine shop among other things. I have a good machanic leading the way but I am networking with you guys to make sure we are not missing any thing or need to look at other possible hidden issues.
Thanks again for any help

 

[dsichewski]

just thinking, since you have the machine down. might be a good idea to check the make up valve and line reliefs for the stick circuit??? just to make sure nothing is stuck around them? Sounds like you have a good plan of action as the above have mentioned!

 

[Lee-online]

I have seen this way too many times, mostly on the 315 bucket circuits and early so it was covered under warranty . what happens is the nut on the cylinder piston loosens and it then hammers the washers between the nut and piston. this debris then enters the system.

It usually destroys the valve and spool but metal does get caught in the slow return check, cooler bypass, return filter and return filter bypass.

Hopefully you get all the metal out and get the spool to move without causing too much of a drift problem

 

[Chris5500]

Are the peas ball bearings?

 

[wolf44]

no they are little pounded pieces of what looks like a ring or a spacer. They have machine feed tool marks on both side of the little pea sized piece. They have been almost burnished to a polished state.