I recently removed the front seats and carpet from my 1983 300sd to track down a water leak that turned out to be from a rotten AC condenser drain hose. I took up the sound deadening material from the driver's footwell, and a good bit of the rubber coating from the rear footwell to assess and remove any rust. Thus far, all the corrosion has been superficial, but on the serious side of superficial.

The rusty trail leads to the corner where the rear floor meets the bit of steel on which the rear seats rest. I can see evidence of water having passed through under the seat.

What is the best way to get a look at this area? Removing the rear seat or perhaps cutting a little access hole just above this area? I'd coat the raw edges of such a hole with miracle paint.

I have to ask what the best way is to get to the rust inside the brace that would be below the driver's seat? I wish I knew a trick that would let me get in there to remove any loose rust and take back a bit of the paint surrounding the rust in order to apply miracle paint.

Any advice will be gratefully received.