Before you ask a question, check to see if it's been asked before. We show all the common Transit faults here and it's a good idea to read through these in case they happen to you in the future!!
I have had roof leeks with both TC vans, mine was from the grommets where the roof racks would be fitted. Sealed them both wit waterproof tape, it works well.
All the above will work it depends on your prep work i.e rubbing down, cleaning grease etc for adhesive to bond. Torch on roof felt strip would last lol depends on the condition of the van as to the repair you want
I know this is an old post but worth the try. Does anyone knows if this affect high roof version also? I have a mk6 lwd high roof and yesterday after a long drive there was water everywhere. Initially I thought it might be the windows but then found all these posts. Thanks for the help.