So, I know that the sunroof gasket is not a seal and that water passes by to drain out the perpetually clogged drain hoses but, I'm having a large drip into the trans hump behind the console in the rear seat as of late.

My 11 y.o. gasket is sunbaked in FL and a bit alligator skinned-could it have shrunk enough to allow such a leak to increase? I see my headliner core, not the fuzzy material, sagged about 1" off the roof a that point-this was like this when I bout it 2 years ago with 9k miles. Maybe it's an old condition.

 

I would blow out the drain hoses first, then watch to see if the interior leak issue disappears. In more than 9 years of ownership of my 2005 S-Type, I have had to blow out my drain hoses twice....

 

I've not had the S-Type headliner down and/or sunroof apart, but have done so on several X300's. On the X300, there is a tray attached to the back of the sunroof, that moves for and aft with it. It spans the gap from side to side. It's purpose is to direct drainage water to the gutters running fore/aft at the sides, for further drainage out the (possibly clogged) hoses. It is not unheard of for said tray to traverse back with the sunroof...and then hide back there...never following the moving roof forward again. This would leave a gap across the middle of the aft edge of the sunroof opening for possible leakage. Is this perhaps just above the driveshaft hump where you are experiencing leakage?

 

Excellent report. This one is now 11 y.o. and likely never had the hoses blown, so to speak.

Now for the involved job...

 

It is at the back of the sunroof. My headliner core is down about 1" off the roof, enough to stick fingers into the gap and ostensibly from water over the years-I got the car that way. Should I be able to feel that tray with the roof closed?