My 335xi had developed a couple of super annoying persistent rattles in the dash that were bugging the hell out of me. These were the sort of rattles that feel like every single vibration can set them off a-rattling. I hated them so much. Now they’re gone!
I don’t need my car’s interior to be absolutely positively 100% rattle-free, but I at least want to be able to drive down the road and not have every single bit of road texture make a bunch of irritating-ass noise come from the dash. So I went about trying to isolate the noises.
The first noise source was the center speaker grille/vent cover in the middle of the dash. Many people on the BMW forums mentioned this thing rattles like crazy so I wanted to try and fix it. My first attempt at prying it up with a trim tool was unsuccessful. I tried again with what felt like way more force than was safe and was eventually able to pop the clips holding it to the dash.
From here, I first tried to quiet it down with some little stick-on felt pads that you stick on the end of chair legs so they can slide on your hard floors. This didn’t quite do the trick so I went back and instead lined the 3 flat edges of the underside of the thing with stick-on flat foam weather stripping tape.
It didn’t immediately go silent, but after a day or two for the foam to settle, this seemed to do the trick with finally quieting the racket down from the damn center speaker grille. But after a couple cold days, a different rattle presented itself that seemed to be coming from where the dash meets the windshield, right behind the gauge cluster.
I remembered from my attempts to silence the infinite interior rattles of my old Mazdaspeed 6 that folks on the forums for that car suggested wedging foam backer rod (a.k.a. gap filler) between the dash and windshield.
I picked 3/8" diameter backer rod thinking I shouldn’t go with something too thick, but when I went to wedge the backer rod between the windshield and dash, it turned out that the gap between the dash and the windshield was actually kinda big, and that below this point there was a larger kind of sub-shelf that the backer rod basically fell down in to. Here is an extremely detailed MS Paint diagram of this lower area.
I went for a drive after adding the backer rod, and the dash was still rattling from the same spot. I had thoughts of using my trim tool to try and fish the backer rod out and replace it with a thicker one, but magically after a couple days the rattle went away and hasn’t come back!
Even though it’s been maybe a week now since I banished this final rattle, every time I drive my car and the dash doesn’t rattle all the damn time, I’m like, ahhhhhhhh this is so soothing. I guess I didn’t realize how much I hated those rattles even though I knew I hated the rattles. I hated them even more than I was aware of.
There are actually a few other random interior noises that I’ve quieted down in the past with similar techniques, but the dash rattles had completely consumed me and made me pissed at my car. But now, when I hit a bump or some particularly shitty section of crumbling Wisconsin roads, I get a thwack from the tires, and maybe a muted creak or tick noise from assorted parts of the interior, and that’s it!
It’s glorious, I tell you.