My car leaks from the rear taillights and both rear quarter glass into the boot - everything in the boot gets saturated when you go through a auto car wash or drive it in heavy rain, it started doing it shortly out of warranty period.
You'd wash it and the seals behind the quarter glass would deteroriate and leave black streaks down the side of the car, until they completely deteriorated and there's nothing to leave black streaks down the car anymore.
I never bothered to get it fixed cause its in the boot
Water leaks are a real pain in the *** to find, the only way is the garden hose, huge volume of water and get yourself into the footwell to see where its coming from, if you can't see it then its a dash out job and given what it would cost its not economical to do.
If you take the dash out, then replace the heater core while you're there as its a common failure on LV that they also leak.
If the A pillars are rusty thats another cause of water leaks causing the driver side carpet to get absolutely saturated - it gets in then goes down the inside of the A pillar into the carpet - windscreen out job to check, is cheaper than pulling the dash.