to warn fellow owners, the black plastic triangle in the corner of the rear passenger windows hides a sponge which fills a gap in the panelwork.

this sponge gets wet everytime it rains, and starts rusting out the door, hidden by the black plastic.
flakes of rust collect at the door bottom in the sill and rot that as well.

have a look what mess is under yours, its quite simple to take off (hint start on the inside of the door, that black triangle slides up, the outside one then can be unscrewed off). another quick check is just open the door and look at it from the edge, a few inches up from the door latch mechanism, with a torch you can see the sponge and its work.

why would ford put a sponge of all things in a water channel? sound proofing?

That's some random post after three an half years away but damn useful too even tho there aren't any 5door fiesta owners on here I don't think

Surely tho it'll be better in Top Tips rather than noobs!

Mods, fancy moving it????

i am just puzzled why ford would put a sponge alongside body panels, sponges
take ages to dry out, its just a rust magnet.

the only neat thing about a sponge is that it expands and is not messy so its easy for an assembly line guy to pop one in, versus taking out the caulk gun and filling in the cavity.

i removed the sponges from both my rear doors.

do ford put sponges anywhere else ( like the front door window corner, under the mirror?? )

Very random,I will leave it in noobs for now as the op is asking a question

So that means 3dr fiestas use this foam as well.

why didn't they use closed cell foam like polystyrene, instead of this sponge rubbish

and you could say the wind noise is kinda cool, after all this is a Fiesta not a Bently

Odd, how old is yours and how bad is the damage?