Sounds like your e-brake is little jammed. Does your car jerk to one side when you use the e-brake? Try parking up hill and use the e-brake, if it starts to roll then you know for sure your e-brake is not working. You can adjust it if nothing else is wrong with it, hopefully you have no hold down pins that are broken. Two months ago, my hold down pin was broken for the driver side and kept making noise when I use to drive. I thought it was the rims and after carefull inspection, it turned out to be the hold down pin. Not an expensive fix if you can do it your self. You can buy the entire kit from BMW for like $20. If you need to tighten the cable for your e-brake, here is a link to help guide you.... http://www.pelicanparts.com/bmw/techarticl..._Adjustment.htm
Hope this helps...
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Body: 318i 4 door
Mods: M50 engine, Jim C chip, light-weight flywheel, dual cat-back custom exhaust, 3:15 lsd, euro headlights w/angel eyes, 5300K HID, smoked corner lights, FK Motorsports foglights (crystal clear), ABS plastic upper eyebrow, clear side markers, M3 powered side mirrors w/LED, blacked out grill, M3 lighted shift knob, 17" ROH Furry wheels w/Kumho tires, Brembo cross drilled rotors and Hawk performance brake pads all around, PSS9 Bilstein and H&R coil over kit, front strut bar and Alpine alarm.