Rear fender rust prevention
On my 1994 318is the rear fenders began to rust as the dirt and grim would sit on the inner fender lip and retain moisture; and salt in the winter. I now have a 1997 328i that is rust free and would like to prevent this same situation from occurring.
This is what I am thinking of trying but would like some opinions or alternatives.
1. Thoroughly clean the inner lip of the rear fender.
2. If any rust is found, sand to bare metal prime, paint and clear coat.
3. (Option A) After paint job is good and dry, fill the lip with a caulking of some sort so no dirt can sit on the lip and collect dirt and moisture.
3. (Option B) After paint job is good and dry, apply and undercoating treatment (this might be able to be done right over a primer).