Hello, I tried searching but to no avail. Any advice appreciated. If there's already a thread somewhere on this topic, please let me know. I recently bought a late '90's JCB 217S, SN 4xx,xxx. It had some leaky rams, which I had rebuilt and I reinstalled them. Everything seemed to function as it should for a minute, but then I heard a little high pitched pssst and the dipper valve went dead, in both directions. In fact the control lever has a lot of resistance, whereas the others move to the finger touch. (Note: the dipper ram was one of the ones rebuilt.) I was thinking some sort of relief valve caught an air pocket or something, and needs to be reset, but I wasn't able to ascertain with any certainty what that might be. So before I dive into taking things apart, I figured I'd ask. Another theory that just occurred to me is that some o-ring popped in the main valve and is thus jamming the valve so it can't move in either direction, and I'm probably bending the control rods when I try to move the control lever. Thanks kindly in advance.
You have pilot controls or linkage to the valve? Does it make a difference whether the machine is running or not?
I poked around today and it looks like there is a rod connecting the control lever directly to the valve. Thinking back as well, when the valve got "stuck", the dipper kept retracting until the hard stop, and I'm guessing the valve got stuck in that position. I can't totally tell since I got the machine, but it does seem like there is a load on the hydraulic pump, which would be the case if the valve was stuck open, no? It might have quasi closed again, but I'm not sure. I'm beginning to like my stuck plunger/popped o-ring theory, but I don't know anything about these HBPV's and what they do. I imagine a big enough air pocket from the newly rebuilt ram could have looked like a huge pressure drop looking like a burst hose. I'm going to look at the mechanical drawings in more detaiil, next. Thanks
Yes, if the spool is stroked it is blowing over the relief valve. Does it make any difference on moving the spool if the engine is off or on
>Does it make any difference on moving the > spool if the engine is off or on I didn't start her up today, but it didn't yesterday.
Hopefully nothing too serious jamming it up. May also lead to a problem with your cyinder
pull the spool out and clean it look for any trash in the body spool should move smooth with no binding
Thanks all for the input. I started taking the lever console apart to get at the top of the valve body, and indeed, the rod to that valve was bent a fair bit. I straightened it out and noticed as well that the spool was stuck in the "up" position. Just to see what would happen, I pushed the lever forward while keeping it from bending again with my other hand, and that produced enough down force on the spool to pop it out of its stuck position. It started working again as normal. I don't know if something was in there that then flushed through, or if it might get stuck again. I'll keep an eye on it, but it's working for now. Short of that though, the disassembly plan was to clean the valve body and then disassemble that one valve, which appears can be done by removing some retaining plates from above and below it. I presume the spool comes out at that point.
Make sure the front loader is not in float position. I learned that while having similar issues on a previous backhoe. Once front bucket was out of float position the rear hydraulics worked great but minimal to nothing while in float. Not sure if our JCB have a float position or not but my ford did.