Bobcat S300 aux hydraulic issue

[05sprcrw]

On my S300, I have one aux hydraulic coil I think is either not turning off or come crud is in it. I thought I would check and see if anyone has had a similar issue.

This came up last year a little bit but found a loose coil and thought that was the end of it. This weekend I was using the grapple attachment on it and when I would raise the grapple it would stay up like it should when I started, but by the end it would stay up as long as I held the paddle switch to the right.

If I let off it would go back down slowly. If I push the paddle switch to the left it would go down normal speed. It seems to me like the stems and coils must be functioning correctly since it operates normal. Only other thought was possibly the switch itself but I don't think they sell just the switch, and I would have to buy the handle assembly instead.

Anyone come across this or have some ideas?

 

[crewchief888]

Sounds like you may have a stem sticking partially open.
Possibly a broken aux stem centering spring
Or a cylinder thats bypassing internally

 

[05sprcrw]

I won't rule out a cylinder but they are new cylinders that I just put on the grapple (converted a bucket over). I have not pulled the aux stems yet to check them out, hopefully tonight or tomorrow I will find time to check that. Is the spring in the aux stem something I can buy separate or is it part of a larger assembly?

Thanks

 

[crewchief888]

The stem is an assembly.
The springs I'm referring to are on each end of the aux spool that keep it centered.
They rarely break, but I've seen it happen. What you can do is swap the aux stems around, and see if the cylinders keep drifting down. If they don't, is guess the problem is the stem sticking partially open.

 

[05sprcrw]

I took the stems apart this weekend and cleaned them but I didn't find anything out of the normal on them. I put them back in and it still drifts one way. I am going to try and find time to take the spool springs out and make sure they are the same. I ohmed the coils and both were around 5.1, one ohmed a little higher before settling in at 5.1 and it has some exposed wires at the base of the coil. I am going to order one coil to replace that one just to make sure that isn't the problem. I am hoping to find time tonight to try pulling one coil off at a time and just seeing if I can get it to stop to take the control out of the equation as I am starting to suspect the switch itself.

 

[05sprcrw]

I finally got parts and took the spool out of the valve and put new o rings, springs, bushings and the washers in the valve and it still drifts. I am not sure what else would do it if I unplug the coil on the side that is the issue, the grapple still drifts shut, so I feel like it is in the stem not sure what else it could be, so I am ordering a stem today and will try swapping the new stem in and hopefully that will solve it. If not I was wondering if you guys had any other ideas. I feel like there are only a few things that could cause this, only other thing I could think would be if the spool shaft wasn't exactly the same from end to end and I put it in backwards?

 

[63 caveman]

05sprcrw,
You have done a good bit of work on this. I would make sure that the "new" cylinder is not leaking internally before going deeper into the controls.

 

[05sprcrw]

That is a good point that I have not thought of, very well could be a cylinder bypassing, that will be my next test. I have not had a chance this week or last weekend to mess with it. Hoping to find time this weekend.

 

[3rdgendslmech]

You could do a few things to see if your new cylinder or the other cylinder is actually bypassing.
After it's been worked for a while, I'd say 20 minutes or so, one cylinder will be warmer, or actually hot to touch. A temp gun can be used. Bypassing oil creates heat.
Another thing you could do is have a helper listen for a "hissing" noise inside the cylinder. A mechanics stethiscope or a long prybar with you your ear to the handle works pretty good too.

To try to figure out if your spool isn't returning to center or neutral, swap your hoses on your quick connect fittings. If it's drifting down due to the spool, then it'll be wanting to open up if you swap the lines around. It'll work backwards so just be carefull if you're working in tight quarters....

 

[05sprcrw]

I finally had some time to work on this, and it is still doing it. I swapped line ends and while it doesn't push the grapple open you can see that it slacks off the pressure. One way if I go against the relief it will hold tight and not "loose tension" the other way that drifts will hold tight as long as I am on the paddle switch. Once I let off the switch it will go slack and the cylinders will just slightly drift, enough you can see the rod move. I switched it to another attachment and the same thing would happen with it. So I am back to looking at the 300.

I did replace one stem and coil because I thought it might be that, but no change. Does the aux have a load check like lift and tilt functions? Or is this just the way it works? I feel like it might only hold the pressure one way and bleed off the other?