I suspect there are more than one rattling sound. I, too, wrapped and tied the valve, with little effect.
There is less rattle with two people on board, and, most of all, the sound disappears when I reach back and pull on the roll over bars(!).
Are they touching the alu body where they pass through it, maybe?
I have the luggage rack that I installed using different clamps on the roll bars. They still use the cotter pins to hold them in place. Drove around and noted the constant rattling of something. Segue to my placing an umbrella on top of the gap between roll bar and rack and using a bungee cord to tie it down. Rattling disappeared! The right roll hoop was the culprit and this just clamped it out. Now the cotter pins make a smaller rattling noise as the entire rear of the car flexes. I've so gotten used to noises from this creature that when they disappear I have to assume that whatever was making the noise broke or is no longer attached to the car... and I should probably check my mirrors to look behind me.
