I pose a question for everyone with roof rust to please respond.
Before you noticed the rust did you have an issue with water leaking inside the car? My theory is that it only happens on cars who take water into the inside. That would be the only way moisture on a regular basis could get inside the car to cause the rust.
My old Colt was completely dry on the inside, no leaks at all, and had pretty bad roof rust. My current one leaks in both the driver and passenger footwell (quite bad, haven't found where it's coming from yet, suspect it's a windscreen-out job to repair), and it also has bad roof rust. I've noticed with the leaky one, the rust is spreading alot more rapidly though, it has gotten quite bad over the past 6 months as it has been sitting outside in the weather, so it's being hit by both rain/sun on an almost daily basis (NZ weather - 4 seasons in 1 day
I need to fix this soon, as I don't think i'll pass my next half-yearly safety inspection. What would you guys do in this situation? I think it's gone beyond the stage where I can bring the rust back to bare metal and rustproof the inside. A roof swap would probably be the best (and most expensive) idea right? Would it be worth having it cut out and new metal welded in?