I'd check it and/or clean it with Throttle body cleaner and test it. You should be able to "blow" out from the side that is screwed into the engine but not be able to "blow" into the nipple end. Wow, that sounded weird. :shocked: But I think you will understand what I mean when you unscrew it out from the valve cover.
I reserved myself from stating "When water doesn't flow through it anymore." but I spared ht_addict and figured I'll just provide a short Optima Forum Webinar for the educational experience. There's a few on this forum that could use this since PVC is used very often.
Next, will be my Dyslexia Webinar in case they don't see anything wrong with it spelled that way. :lol:
I feel I need to add that a PCV valve rattling or not has nothing to do with whether it actually works or not, just whether it's mechanism has seized one way or the other (which could be open or closed).
Looking inside of it from the thread side, the inner circle should be centered and stay centered. If it doesn't, then it's a sure sign the pcv valve has gone bad and will be leaking (the spring has sprung). You can do a rudimentary home test with a bike pump and a balloon, putting the balloon over the blue side and using the bike pump on the other side. The balloon should inflate and stay inflated llwoth the pcv valve acting as a one way valve