Hi JJ, new to the forum but have been reading awhile. I would like to know a little more about this ck valve. It looks like a quick fix to a common problem a lot of us are having with our CUTs. I have a ck30 and it leaks down fairly quickly. It may be still under warrenty but from what I have read here, it will probably be in the acceptable range. Any info greatly appreciated.
It is difficult to understand why a certain valve will not leak for a long time, and then some new valve leak from day one. I don't believe the manufactures test each valve, they only test a few out of a batch, unless you are talking about Mil-spec type equipment, where I believe each item is inspected and tested. That is not to say that it will not leak, but it did meet acceptable standards under testing.
If a valve is leaking down and causing problems as in using the bucket as a platform for work, that is not good. However, not many people leave their lift arms/bucket in the air. Yor would not normally leave the bucket in the air for safety reasons anyway. If this leak down is not acceptable, then you have to repair the valve if that is possible, or replace, or put a pilot operated check valve in the line. The way the check valve works is this. When your valve is in neutral, there is ball or poppet that blocks fluid from returning from lift arm down pressure caused by the weight of the bucket, and or load. the ball is kept in check until you apply pressure, about 600 lbs, and that will release the ball for fluid to flow normally. However if your bucket is also dropping, it could be that the weight of the bucket is acting like a ram and causing the bucket cylinder to bypass. You could also use a check valve in the bucket circuit.
You may have read about valves with load checks. What they are referring to is that there are load check in the valve to keep the bucket/lift arms from shifting when you go from up/neutral/down on the control valve.
So, there are four things to think about, accept the leak down, repair valve, purchase new valve, and install load checks, which is the most secure way to solve this problem.
http://www.surpluscenter.com/item.asp?UID=2009022607084017&item=9-1343&catname=hydraulic