I put a new activated charcoal filter in my W210, and I can smell things from outside. I refitted the old one to check, and I could still smell fumes from other poorly maintained vehicles.

I don't have automatic climate control, its manual controls only, with aircon.

The filter can only go in the one way, and has a thin foam strip around it's circumference.

Am I missing something? I replaced the old one because of age and airflow, although the old one blocked all external fumes perfectly before I removed it. Has anyone else had this problem?

The part is 176, on here:



It slides up into a recess, and is covered by a plastic blocking plate (170/173)