The PVC should always have a bearing inside of it. If it was hollow it would serve no purpose of venting it would just vent all the time and not when pressure built up. It may have been faulty from the factory or if you replaced it prior it might've been a bad one from the store. I've replaced my PVC on my truck and the piece of garbage broke before I put it on. Fram, wix, and microgard all make faulty stuff. If you don't hear a rattle its bad.