I know we are pm'ing about this..
but I think your rattles are beyond just the third brake light one... honestly, next step, remove that shelf. everything prone to rattles unveils itself (and theirs a whole heck of a lot if any of the little plastic fasteners of tolerances when the deck was made/installed were not adhered to....it is a Honda, not a VW Phaeton.
Things you can do w/ rear deck out..
1) wrap underside w/ a thin layer of damplifier/sound deadening type stuff..there are spray sound deadening options, but w/ both applications, you want to make sure fastener points and areas that need to be exposed to allow the deck to go back in, stay exposed. some people
2) ace hardware sells black adhesive backed felt ... I used this on exposed metal tips, in between panels that seemed they could in the least bit be prone to contacting each other and along the edges of all the plastic contained in the rear deck.. I honestly think a couple of rolls of this tape should be given to any new owner.
Here's some on amazon..
I only had to do the above steps on my '08 ( that was built in August 07)... my '10 had buffering and felt tape applied in the rear deck...not as much as I would have laid down had I gone to town, but the amount that should have been applied to all 8th gens to begin with (guessing so many service department check in's related to rear deck rattling finally became a nuisance to dealership owners, honda took notice? i dunno)
Some people have utilized that expanding foam stuff meant as a insulator for around the home (spray into crack, seams, etc...expands and dries hard)...I always like to be in control of where stuff is applied, so I personally wouldn't go this route..not saying it doesnt work and actually might be a quicker (and could also prevent the need to remove rear deck if sprayed in certain spaces).
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