



appears to be in a double skinned area (?? not 100% sure feel around the dash board end and you'll see what I mean) behind the dashboard, that corrosion is quite surprising for a car with wheel arch liners and I am guessing as it's a 1300 that it has no sunroof. I suspect you might find that the square reinforcing section that runs under the top of the front wing is rotten this is typical of the early coupés that had no plastic inner arch liners but rare on later cars. I'd be inclined to remove the wing and investigate further it'll be safer that way anyway as otherwise you will not be able to see any areas that are getting overheated whilst welding
Hi,
Thank you for the photos ;-)! Today I analysed it closer. The rust is on the top plate of a hollow section - that runs inside the car, not behind the front wing ( I looked behind the front wing and it seems to be in very good condition without any rust).
I broked through the rust and looked inside the hollow section with mirror and lamp. Fortunately it seems to be only a local problem. My car has a sunroof anyway

and also plastic inner arch liners. I think that the problem was caused by the top plate under the windscreen. I can see handpainting and rough handfilling on it. Maybe it was rusted and the water reached through the rusty hole this hollow section and because of leaves and dust the water couldn't flow away.
It will be a very hard work to weld and repair without taking the car apart

..