body and interior What Does It Do

[1972-2002]

what is the purpose of the tube that originates at the top of the gas fill tube and runs forward to the front of the car. not sure where it ends up. it is 1/4" diameter and clear.

 

Garry

[Koblenz]

Others can chime in. 

 

I believe it was a "gas fume" vent that goes (or did) to a charcoal filter in the engine bay area.

[jgerock]

Many threads on this topic.  Here are some graphics from RealOEM.

 

[TR]

On my 73 tii the tube ends up connecting to the air cleaner.  Obviously this puts vacuum pressure in the tube so fumes would be sucked out of the gas tank fill tube and drawn to the intake system.  Not sure why BMW did this but I am pretty sure this is how my tii was set from the factory.

 

TR

[FunkyLaneO]

It is part of an evaporative emission system, the fumes from the gas tank are routed through a tank (that allows vapor to condense and drain back into the tank) then to a charcoal filter (that filters the fumes to an extent) then to the air cleaner (where the remaining fumes are sucked through the engine and burned up)

 

The euro spec cars vented directly to the atmosphere (which wasn't very environmentally friendly)