I was checking for a bad rear wheel bearing (yup, got one), and when I went to jack up the rear of the car on one side the body made some crunchy noises and some rust dropped out. I looked around very briefly and it looks like its rusting right in front of the rear wheel. The rust hasn't reached the outside of the body yet - any tips on how to stop it before it becomes a problem (problem meaning cosmetic)?
Do you mean the sill? Is it structural or cosmetic? Where in the World are you? Would the car fail its safety test with such rot? Is it due to a bad repair previously?
Not much one can do at this point. Cut out the offending area, weld in new steel and refinish. When the car was new, it might be that the dealer did not put in the vinyl "plugs" that seal the shipping tie down holes in the rails in the front of the rear wheel wells.
North Carolina. Not a previous repair. It is not structural. It is not cosmetic... yet. I'll snap some pictures when I'm replacing the wheel bearing. I'm guessing getting in there with some POR-15 or some other rust stopper/converter is about all I can do at this point. Car has 162k on it... if I can make it last to over 200k before it makes it through the outside surface of the car, I think I'll be ok with that. If it looks difficult to stop, I may sell it soon before it becomes a major problem.