I have had this sound forever but I never thought to bring it up here. After I turn off the car I sometimes get this knocking sound like someone is knocking on the metal. It is always 3 knocks and it is coming from the rear passenger side near the below the gas cap. I have brought it into the dealership and they have found nothing. Does anyone else have this/ or have heard about it.

 

Its just your fuel pump,its normal

 

That's just your drunken trunk monkey, you're good dude.