Z4 rare problem? engine noise from firewall; dash/footwell
Z4 2007 40k miles (posting this issue on a few different BMW forums as it seems to be rare and after lots of searching have not found any fixes)
Day 1 relatively loud fan noise coming from behind/under/inside driver's side dash near headlight switch. I made sure the air conditioning and fan controls were off. Never really heard this particular fan noise before; I'm assuming it's the e-box fan. Also, no air flow was coming out of that driver's side vent and its definitely not the same fan noise and origin as the climate control fan.
Day 2 The fan noise is gone. I can now hear engine noise coming from the same general area of the dash. Louder than engine noise anywhere else in the cabin of the car. I'd describe the engine noise sounding like a vent or flap has opened up between the inside of the dash/driver footwell and the engine compartment and is letting noise through.
Day3 same noise coming through driver side section of dash. Sound can't be heard with windows down. Sound can best be heard with engine RPM's over 2k+; gas pedal engaged while driving; and windows up.
There are no strange noises coming from the engine with the hood open. The engine noise coming through the firewall into the cabin is just louder than normal in that area of the dash. Sounds kind of like the door or window was left open, but the door and window are shut and the noise isn't coming from the door or window but the dash area.
Does anyone know if there is a vent or opening in that area of the dash/footwell that perhaps allows the e-box fan to ventilate the e-box and if this vent/flap perhaps got itself stuck open?