on mine there were 2 sources of leaks, 1 was the seals round the rear lights and the other was the rubber seal around the rear window. the rear rubber needs a good squirt of sealant all the way round it otherwise it will never seal right, if the roof has been done recent and no sealant was put in then thats why. you need to use a special type of sealant that doesn't go off as such, rather than boggo silicone stuff