[KD07]

So like I said earlier, I started the car this morning and immediately ran to the back of the car, got on the ground, and checked the valve from outside the piping. I put my finger on the metal pin between the valve and the little motor and sure enough, the rattling went away when I held the pin still.

Haven't had time to consider a solution yet, but it shouldn't take much. Not saying this will be the cause of everyone else's rattling problem, but definitely worth checking out first. Also, the valve is on the driver's side, so not sure what could be rattling for those of you claiming it to be coming from the passenger side.