Just got back from the parts counter at the Mazda dealer, and the new 323 GTX PCV valve I bought has a metallic rattle to it when shaken, and doesn't seem to respond well to the blow test (some air comes through the big end when blowing into the small end). It sounds like something is loose in there. Is this normal?

 

It should act like a check valve, good flow in one direction, no flow in the other. If that doesn't work right then take it back and try another.

 

Yes, they make noise. If you're blowing into the manifold side and it's coming out the crankcase side something is wrong. Better yet- set your compressor regulator to say 20psi and try to blow through it "the wrong way". It shouldn't leak. That's how I confirmed my supra pvc valve was bad, and confirmed an old stock Miata unit was good.