After chasing down multiple water leaks in my 2002 M5 (thanks for all the posts about door vapor barriers, sunroof drains, seals around the cabin air filters and associated drains, etc) I'm down to these last two, which are small rust holes in the firewall just behind the drivers side gas and break pedals. see pic below. If I pour water into the compartment under the cabin air filter (note: drain hole for this compartment is clear and drains properly) water immediately flows from these two rust holes in the firewall into the drivers footwell. I removed the quarter panel to try and get access to the two rust holes from the engine side of the firewall, but they are behind the metal compartment under the cabin filter. And looking at a pic someone posted of their M5 with the engine removed, it appears I would not be able to get to it from the other side of the compartment or below it. I would really like to get access to these holes on the other side of the firewall so I can properly (and permanently) repair them. If I only repair them from inside the cabin they will surely continue to rust and become a problem again. I do realize that repairing leaks above this area (i.e. the seal around cabin filter assembly, clearing drain holes, replacing windshield cowel cover, etc etc) will hopefully prevent water from running down the firewall and into these holes, but I don't want to fix just part of the problem. When the next seal starts to leak again in a few years it will start leaking water which will run down the firewall again and continue the corrosion process. Does anyone have any suggestions on how to properly repair these two rust holes?
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