This one is driving me bonkers.. there is a weird rattle somewhere in the boot that I can't pin down so I'm wondering if there are any common "Oh yes, that bit always comes loose" things to check.

So far I've ruled out the boot cover blind (by taking it out) and that's about it.

It doesn't really happen over rough ground, but rather tends to happen when the cabin "rocks" (so if one wheel goes over a speed hump, say) and sounds exactly like the anti-draft flap in my bathroom extractor fan when the wind is blowing hard (you know, that plastic 'clack' noise).

I've had a poke around in the inspection flap on the drivers side where the electrical gubbins lives and nothing looks like it's swinging free in there, either.

Stumped, and because there's usually just me in the car, it's hard to be crawling around in the boot while it happens  2014 BMW 530d Touring, 2006 BMW 650i, 2018 Mini Cooper S

Could be the spare tyre underneath the car is a bit loose?

Have a look at your rear anti-roll bar bushes, as that what it turned out to be on mine  MY08 RR SPORT3.6TD V8 FULLY LOADED, COOLER BOX, GVIF UNIT, PIONEER AVIC-F980DAB HEAD UNIT, RETAINING 4X4 INFO OEM SCREEN AND TS-WX130DA SUB
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I do know the ARB bushes need doing - they creak something rotten .. maybe they are starting to slap a bit, too, good call.

idi wrote:

Could be the spare tyre underneath the car is a bit loose?

It could be .. except there isn't one Missing when I bought the car and I still haven't gotten around to sourcing one I really must! But maybe the winch has come loose.. 2014 BMW 530d Touring, 2006 BMW 650i, 2018 Mini Cooper S

If the spare wheel winch was wound up without weight on it, it will probably be unserviceable and will need replacing as well.

Ironically the retailing dealer fitted it new when I picked up the car (because the old one had been cut off some time previously - 2015 judging by MOT history), but wound it up with no wheel on it because they refused to also source a spare wheel... 2014 BMW 530d Touring, 2006 BMW 650i, 2018 Mini Cooper S

Could check a rear harmonic damper isn't touching a exhaust tailpipe, not unknown but think it tends to be more of a knock than a rattle with this.

Cheers
Col

Hm yeah - this is a really "plasticky" sort of slap/clack noise.. honestly if you've ever heard an anti-draught flap on an extractor fan, exactly like that.

Probably turn out to be something from the previous owner that's fallen into a cubby/crevice somewhere .. if it's anything like the last thing I found from the previous owner, drug paraphernalia!  2014 BMW 530d Touring, 2006 BMW 650i, 2018 Mini Cooper S

Have a play with the damper/stops on the boot to see if it gets better or worse. Also check the spoiler is secure. 2019 5.0 SC SVA (Current)
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I came searching for the same. I have a rattling coming from the boot. I believe it’s the plastic construction attached to the inside of the tailgate. I’m going to take it off, see if there’s something obvious and/or add some sound deadening as a start.