I have a 2018 M3 and 2021 MY. Today I replaced the cabin filters and thought I would share some observations. There are good videos on how to replace (and clean the coils) but haven't seen what I've done.
TL;DR I JB-weld glued a bolt to my 2018 filter cover screw and I used a carbon filter and double sided take to try and keep moisture off the filters.
2021 Model Y
Same T20 screw and same stinky feet problem, but they moved the screw to the bottom of the lid making it MUCH easier to remove. After just 2400 miles the bottom cabin filter was already discolored on the bottom of the filter. This indicated to me that the primary source of the problem is water pooling around the bottom and soaking up through the filter. I thought about how I could keep the new filter from touching the bottom using what I have on hand. I didn't want to do something that might come off or apart and get stuck.
What I ended up doing was cutting a length of carbon filter that would wrap all the way around the filter outside edge, including the tab. I used double sided tape (between carbon strip and the cabin filter) to keep the carbon strip from moving around. No chance of losing it because I will be able to pull it up and out with the tab. It fit fine, the second filter was a bit tighter fit, but I think that is mostly because the carbon "caught" the filter and didn't let it slide in as easily.
My theory: The carbon filter will not soak up moisture like the paper/fuzzy filter does. The double sided tape will also create a moisture barrier between the carbon and cabin filter.
Only time will tell, but maybe others will have a better idea to test. I also thought about ways to try and keep some spacing/barrier between the metal coils and filter, but there seems to be very little space to add anything there, hope someone has something to try.
Edit: I didn't see a leaf inlet cover for the frunk, the 2018 and 2021 model 3 are different shapes and the 2021 Model 3 leaf filter didn't look like it would fit on my 7-seater 2021 MY. So I took the same carbon sheet and applied it to the bottom of the frunk cover (no tape) by cutting some holes to go over the clips.
Model 3
Took the opportunity to make the higgen T20 screw into a thumb screw. Borrowed ideas from other posts but kept it simple and just JB weld glued a bolt onto the end of the screw (no drilling / cutting, etc.).
Source of the problem?
It seems like some people don't have this same problem. I'm in Austin, TX and have an attached garage. My garage is a warm 85 degrees but not air conditioned. I believe the warm humid outdoor air when it comes into my garage cools down which raises the relative humidity. So for most of their lives the cars sit in relatively higher humidity than if they just sat outside.
TL;DR I JB-weld glued a bolt to my 2018 filter cover screw and I used a carbon filter and double sided take to try and keep moisture off the filters.
2021 Model Y
Same T20 screw and same stinky feet problem, but they moved the screw to the bottom of the lid making it MUCH easier to remove. After just 2400 miles the bottom cabin filter was already discolored on the bottom of the filter. This indicated to me that the primary source of the problem is water pooling around the bottom and soaking up through the filter. I thought about how I could keep the new filter from touching the bottom using what I have on hand. I didn't want to do something that might come off or apart and get stuck.
What I ended up doing was cutting a length of carbon filter that would wrap all the way around the filter outside edge, including the tab. I used double sided tape (between carbon strip and the cabin filter) to keep the carbon strip from moving around. No chance of losing it because I will be able to pull it up and out with the tab. It fit fine, the second filter was a bit tighter fit, but I think that is mostly because the carbon "caught" the filter and didn't let it slide in as easily.
My theory: The carbon filter will not soak up moisture like the paper/fuzzy filter does. The double sided tape will also create a moisture barrier between the carbon and cabin filter.
Only time will tell, but maybe others will have a better idea to test. I also thought about ways to try and keep some spacing/barrier between the metal coils and filter, but there seems to be very little space to add anything there, hope someone has something to try.
Edit: I didn't see a leaf inlet cover for the frunk, the 2018 and 2021 model 3 are different shapes and the 2021 Model 3 leaf filter didn't look like it would fit on my 7-seater 2021 MY. So I took the same carbon sheet and applied it to the bottom of the frunk cover (no tape) by cutting some holes to go over the clips.
Model 3
Took the opportunity to make the higgen T20 screw into a thumb screw. Borrowed ideas from other posts but kept it simple and just JB weld glued a bolt onto the end of the screw (no drilling / cutting, etc.).
Source of the problem?
It seems like some people don't have this same problem. I'm in Austin, TX and have an attached garage. My garage is a warm 85 degrees but not air conditioned. I believe the warm humid outdoor air when it comes into my garage cools down which raises the relative humidity. So for most of their lives the cars sit in relatively higher humidity than if they just sat outside.
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