i know its nuting like a BHG, or a knock but it is something weird, when i drive the car if not fully warmed up the first few feet sometimes i get a little hissing noise , its weird but goes right away and if i do warm car good i never get it, and yes i almost always warm up car unless its really warm outside but i do let it run to get oil though the car, also where should the temp gauge be at and the oil pressure