We had a real downpour last night, and while I was in the X5 testing android apps & peripherals for my "gauge substitute" project
https://xoutpost.com/bmw-sav-forums/...le-gauges.html, I noticed the carpet underfoot was wet. Despite having several such storms during my brief ownership period (5 months now), there have been no other leaks.
The carpet shows signs of water draining down from behind the dead pedal; I'll try to remove it to see what's behind there.
I've never used the sunroof, and removed the fuse for it previously, so there's been no movement of the glass up there, so likelihood of suddenly developing a drain leak (along the front left A-pillar, which shows no moisture) is low, IMO.
I did disturb the firewall plug above the footwell when running wiring for my electric fan installation, but I sealed it thoroughly with pest-proof Great Stuff foam spray, months ago. No leaks before now, and the carpet on the toeboard is dry, directly under the plug, and the firewall area was completely dry underhood, on both sides, as well.
I also checked the drivers door drains and the sill area; no moisture anywhere, either, and so I suspect another area...the bottom of the windshield where the seal meets the body.
On both sides, the seals meet at a crack/hole that seems a logical drain to me. Mine were filled with tree debris (X5 sits under oak trees), and were wet, still. I'm unfamiliar with the bodywork, seals, drains, etc. on this vehicle, but might my wet carpet originate with the left side "drain" hole? My X5 sits tilting forward and to the left, making most drainage flow in that direction. I blew all debris clear before taking photos:
dry toeboard next to dead pedal
door drain and door sill area both dry