How can i check if there is rust in the roof?

[Emm3]

My car has one or two marks on the roof, its a bit hard to tell what it is as it may be bird crap thats stained the paint but then again e30's suffer from rust in the roof so i'm worried about that too. I want to check this if possible but don't want to start pulling the headlining off. There is no bubbling or anything on the surface.

[M3Jim]

If you have a sunroof, just remove the panel. It's about a 5 min job! And shine a torch in there and you will see.

[mikey75]

As M3Jim said best thing is to remove the sunroof, I've just removed the sun roof on my 325i, found quite a bit of rust at the back of the roof, no rot formed so think I've caught it early enough. Just need to find a way of sorting it out as it's not easy to get to!!