My cabin air filter threads where stripped so I ordered some Brass Press-Fit Expansion Insert for Plastics from McMaster.
1- Drill the plastic thread with the adequate drill bit size (1/4") according to whichever insert you ordered.
2- Use some type of glue for plastic to make it stronger.
3- Push/hammer the insert inside the drilled hole.
4- Done.
Materials that I used:
- Brass Press-Fit Expansion Insert P/N: 94510A050
- M6x1 Screw P/N: 98093A436
- JB Plastic weld
Note: I would not recommend getting the same insert I used because I found out they are a little too big. It would have worked better with a smaller one.
A better one to use would be:
- Brass Press-Fit Expansion Insert P/N: 94510A045
http://www.mcmaster.com/nav/enter.asp?partnum=94510A045
- M5x0.8 screw P/N: 98093A312
http://www.mcmaster.com/nav/enter.asp?partnum=98093A312
Edit: Fixed screw part number mistake.