I have a Coleman Destiny popup camper that was made in 1993.  We noticed it had a roof leak last year.  The only possible "openings" are 4 bolts through the roof where a bike rake is mounted and the rubber stripped seam running down the middle of the roof.  I caulked around the bolts and sprayed a rubber sealant down the seam.  With the rain this year it is still leaking and water has somehow gotten under the sealant on the seam and is bubbling up. Does anyone have ideas?

http://www.eternabond.com/RV-Leak-Repair-Products-s/22.htm

sometimes the canvas will fail to the point where the waterproofing does not work, especially at stress points. you cannot always see it.

about all you can really do is cut out the bad spots and sew in some new canvas. not really a DIY type job since you need a serious sewing machine to do it.

it might even be time to consider replacing all the canvas.

ETA: I realized you are probably talking about a leak in the part of the roof that is solid and not canvas.

Ya.  Its the hard shell top.  So far the canvas is good.

I have a small leak in our pop up.  I inspected and found a small spot that had corroded through where a mount bold for the roof top bike rack is mounted.

I've been thinking about using that Flex Seal stuff (from the commercials) to see if it seals it up.

If it works good, I was going to seal all the roof seams with it to stop any future leaks.

I figure hell, if they can put it on a screen door in a boat, it should stop a leak on a trailer.