A serpentine belt tensioner can create a knocking noise when it is worn out and can no longer dampen the pulses that occur as the engine fires. Hopefully that’s all it is. If not, I’d suspect a sticking hydraulic lash adjuster.So after 2 weeks they finally called me this morning. They are saying that the v belt and tensioner needs to be replaced... does that sound like a possibility of the source of the tapping?