317B excavator stick ram opening up and won’t hold

[Pralhad Birdi]

Hi all,
I’ve got a 317B that we recently replaced cylinder seals on. Before replacement, machine was okay and didn’t have any hydraulic issues apart from external leakages (which necessitated the seal replacements.)
All other cylinders were fine after the replacement, but the stick cylinder would open up by itself when retracted and under no load.
Disassembled the cylinder, and found the seals had been damaged upon installation. Changed the seals, and issue still persisted.
Tried changing out the joystick for another one as I thought it might be a stuck plunger, but issue still persisted.
Swapped the stick and bucket lines, and the problem migrated to the bucket, so I’m pretty sure it’s a main valve problem at this point.
I’ve got the valve off the machine, and I’ve pulled out the spools etc and haven’t seen anything unusual. On the Stick 2 spool however, on opening the bottom spool cap, the spool has threads at the end and a convex washer, but no bolt holding the washer on. Is it supposed to have a bolt on it, and is there anything else I can check?

Thanks

 

[Nige]

I’ve got the valve off the machine, and I’ve pulled out the spools etc and haven’t seen anything unusual. On the Stick 2 spool however, on opening the bottom spool cap, the spool has threads at the end and a convex washer, but no bolt holding the washer on. Is it supposed to have a bolt on it, and is there anything else I can check?

Without a Serial Number to work with, the question will remain unanswered.

 

[heymccall]

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Whole view

 

[Pralhad Birdi]

Without a Serial Number to work with, the question will remain unanswered.

Sorry, my bad
Serial number is 4MM00179

 

[Pralhad Birdi]

Top
View attachment 357890
Whole view
View attachment 357891

The cap on the bottom is quite a bit longer than in this diagram.
The rest of the caps on the bottom of the spools look like this, but this one has a longer cap and a spring in at the bottom.

 

[Nige]

See attached. The one you are looking for is shown as "Section A-A"

There are two types of that valve. By machine Serial Number you should have Type 1. The difference between the two is the P/N of the spacer.

 

[Pralhad Birdi]

See attached. The one you are looking for is shown as "Section A-A"

There are two types of that valve. By machine Serial Number you should have Type 1. The difference between the two is the P/N of the spacer.

Turns out my guys on site had taken out the spool from the bottom, and put it back in the wrong way round. So the diagram helps to clear that up.
But the initial issue still remains, as the spool was only removed after the stick started releasing.
I’ve opened up everything I can on the valve body in the hope of finding some seal debris, but nothing so far.
The spool is in neutral position as per the diagram when I slide it in.
Any ideas on what else I can look at?

 

[Pralhad Birdi]

Sorted it I think. The relief valve was full of obliterated seal material that was causing it to stay stuck open.

 

[Nige]

The relief valve was full of obliterated seal material that was causing it to stay stuck open.

Disassembled the cylinder, and found the seals had been damaged upon installation. Changed the seals, and issue still persisted.

When I saw that comment I did wonder where all the chopped up bits of seal ended up.