Water leaking into rear well.
My 05 Sienna started leaking water into the rear well on rainy days. At first I thought it was the Large Gasket that goes around the tail gate opening. After carefully examining the gasket and finding no breaks or flaws, I have come to realize that the leaking was around the exterior light just above the rear windshield glass. I sealed it with clear sealant and no more water. I also put some CRYSTAL kitty litter in a pillow case and left it in the rear well to dry out the area. That seems to be working well also. I read that someone else on this forum said he tried everything on his 06 leak in the same area and then tried sealing the exterior light. So thanks for the hint. I also put a bead of sealant around the rear washer nozzle since it is right next to the oblong rear light. Just saying.