I just washed our 2008 Mini Cooper R56 (no sunroof) and when I was putting it back inside I saw some drips of water coming into the car from the airbag cutout on the passenger side C pillar.

I've done some searching but can't really find threads for non-sunroof leaks. Any ideas what would be causing it?

The car doesn't have any obvious rust damage and the external gutter rail looks OK. I found a thread for a different model Mini that said you take the headliner out to access the screws holding the gutter on.

My Haynes repair book has a procedure for taking the C pillar cover off -

• disconnect battery
• wait 5 mins
• remove rear seat
• remove lower seat belt bolt (and replace with new one)
• carefully pry off trim cover near top of panel, remove the screw, then pry off the panel
• installation is reverse

but that may not expose the source of the leak. The headlining removal procedure isn't included in the book.