Originally Posted by aberg83
Any advice on how to non-destructively remove the carpet to inspect water seepage issues?
Here is what I would suggest; first remove the two grills on the outside of the car just below the windshield. Get a light and inspect to see if you have debris buildup. check to see if the elephant trunk on the passenger side firewall isn't clogged. it's a small vertical flat tube which attached to the firewall with an opening pointing south. If that is clogged clean it. that usually is the case when water backs up in the hollow channel where the wiper motor, blower motor sits.
Now the other thing which could possibly be wrong is behind the H-VAC. unit.
If it is leaking from there, you WILL need to pull the HVAC out and pull the carpet back to see where you have rot. there is a seal between the HVAC and body which also deteriorates and can let water and air into the cabin.
This isn't an uncommon problem with e30's. but go the easy route first. you may just have a lake building up in that channel. clear it. Then run water into that area with a hose and see if a buddy can help you trace it.