I have a Dynamic Acera sk250 LC, SN LL09-U0732. 2004. Just had the arm cylinder rebuilt, put it together, ran it on the job for an hour no problems. Than all of a sudden the arm will not stay extended. Leaks down fast. 4to 5 secs. Ive checked joy stick controls,I've swapped #4 and #6 soleniods that are under the tray where the air filter is. Nothing. I've pulled the spools out top, bottom for that cylinder. Moves freely no trash. Not sure what else to check. I am by no means a mechanic. I'm out of ideas. Thanks in advance for any input. Rick
Oh yea! I also extended the arm all the way out and capped of the lines lifted it up and the cylinder stayed extended. No leak down, at all. Cylinder is good
well if you capped both in and out of the cylinder it wont move as its hyralocked. you will need to do same thing but keep the barrell end open, and if oil spills out and stick stays on the ground you cylinder isnt ok.
Which is it, cylinder extended or arm extended? With the arm all the way out, the cylinder should be sucked all the way in....... DK88 is correct you need to cap only one line at a time to test the piston seals.
Ok did that all was good. The only thing I see I didn't take out, is what looks like some type of pressure valve. It's right next to the spool cap on the bottom of the valve body. Looks like it unscrews and has a flat head screw in the center and a locking nut around that, for adjustments. Ran out of time I'll have to try Monday. Thanks for your help so far.
That would be the "Port relief" which also usually has an anti-cavitation check valve in it. That probably has a small piece of stray dirt or seal material in it from inside the cylinder or something that got into the lines when you pulled/replaced the cylinder. If I'm reading the parts book correctly the spool next to it is an "Arm regeneration" spool and may also be something to check, and it's associated port relief.
if you have boom top level and bring stick all hte was in does the stick drop down? kinda sounds like the arm hi / quick return valve has gone bad if it has one, other wise id be looking at port relief.
Yup that's exactly what it was. Port relief valve. Pulled it out and there was a little 1/4 inch piece of seal in it. While it was out I started it it up real quick to blow out whatever else might be in there. Put it all back together. Works perfect. Thanks everyone for your help I think you all will be hearing a lot from me. Lol
I'd do that brought all the way in and it stayed. So it only did it extended all the way out. But your right also, it was the port relief valve. Thanks you.