There was a leak on the inside wall in the attic, the chimney was right up against it. This was always dry in the summer, but winter it would weep through, drip down, freeze, stain, inside. Figured it was the flashing, it wasn’t. Then figured it was the actual roof itself, it wasn’t.
Finally had a chimney guy come out, he was stumped. He added a sealant to the flashing. That didn’t help. Then he sealed the cracks on top of the shimmery, that didn’t help. He said the inside of the chimney liner was damaged. That the insulating blocks has shifted and a lot of the heat was going right through and inside the chimney itself, said it was dangerous and possibly could be causing condensation to build up on the inside of that wall (The chimney is directly against that wall outside). He suggested a liner for safety, and the possibility that it could be causing the leak. $2,600 bucks later, he installed the liner. It seemed to help immediately, HOWEVER at the same time he also applied a coating on top of the crown of the chimney (at my request, based on product reviews online I read of this sealant). Anyway, in a matter of days it began to dry up. Then a week or two later he installed a stainless steel chimney cap as well. Haven’t had a problem since. The whole thing probably cost me $3,600 bucks by the time I was done...liner, cap, flashing, sealant, inspection. Awful experience to spend $3,600 bucks on something like that. I’m just waiting for the next thing to break in this house.