I’m treating a bit of rust coming through at bottom of the front wings on my mk7. I took off the arch lining and found the bottom of the insulator pad inside the wing was wet. This won’t be helping the rust problem! It seems the plastic covering the foam has started to perish and it’s sucking up water like a sponge keeping the area permanently damp. 

Is it best to just remove the insulator pad? Or perhaps I could cut off the damp end and seal the rest back up and put it back inside the wing. I’m presuming its only purpose is to reduce road noise? 

You may find there are holes/gaps in the chassis behind there where water could be forced in when hitting puddles.  (That was the case with a Mk6 I had).  If possible, I would dry it out and then coat it with some sort of waterproof spray before refitting.

Took other side off today and thought I’d pop a photo on. The bottom of wing was packed with mud. Bottom of foam very soggy. Going to remove them for now.