I also own a squeeky 3. There are a few sources. The seat belt that was previously mentioned and the windsheild cowell are two. Also, if you wash the underbody of your car frequently, your bushings may be dried out from the chemicals in the wash. This caused mine to leak, a little spray lube and the problem is gone. Additionally, and also a bushing issue, if the temp drops below 5 degrees farenheit you will hear a crunching noise from the strut tower bushings as well. This is due to the composition of the material, nothing bad will happen, it just sounds like sh*t.