Take the head lining out, spray soapy water on the outside and blow with an airline on the inside, if you don't have an air line set up a sprinkler. they leak at the top of the "A" post, above the tail door through the seam (take the trims of the seams) and also through the roof bar fixings. if using a sprinkler set up some paper wicks inside in the channel around the roof and check to see which one gets wet first and narrow it down that way.