Hey everyone, I've had a knocking noise coming from under the hood when idling and can't to exactly what is causing it. I took it to a mechanic and he said it was a bad idler pulley that was causing it. I had it replaced, but still hear the sound.

I'm no mechanic, but it sounds like its coming from the valve cover on the passenger side (used stethoscope to try and pinpoint it.) I recorded a video so you can hear what it sounds like.

Anyone know what it may be??