I ripped the car apart twice to add greater amounts of acoustic insulation. The car is very well sealed. Panel clips all have rubber seals so the car does not leak going through water.

But the dust still gets in behind panels. I was surprised at the amount. It will get in around edges of windows, through door handles etc. 

Without pulling panels off yet after the last trip, I think I have a bit less dust it the car by pressurizing the car to a greater degree using a higher fan speed with ventilation, but the air filter was full of dust, but that is much easier to replace.

 

A few photos of the extent the car was pulled apart, but after all the red dust was cleaned out. Behind the panels it was seriously red.

https://thegreynomads.activeboard.com/t65443581/car-acoustic-insulation/

Clean with a water blaster and let dry.
Under the van i repainted with a Bitumen sealant
and brushed it heavily into the corner joints.
Around the mud guards I did this from the inside using a silicon sealant that only skinned and
stayed soft and pliable , I cannot remember the name ,but it came in a cardboard cartridge.
Lots and lots of work , the dust, slowed down seeping into the van, but it will always get in.
I am about to reseal with the underbody protection again ,but more for protecting the ply
than stopping the dust.
good luck but as Mrs Marsh said" look it does get in"

Fred Worthley & Son Pty Ltd in Wingfield, Adelaide is where I get my supplies from ,there is an
ex caravan repairer their, that is on the front counter, he is a world of knowledge, give them a ring and ask, they are very helpful
ring even if you are not in Adelaide, they will give you a name of the product

cheers bob

A few good ideas there, thanks.

Joe.

Good ole Sikoflex .Ive used floating floor boundary insulation under floor, around fridge . Held in place for double sealing with sikoflex ., Sets like rubber . Way better than silicon !!