On my way home this evening in my 91 535i noise started coming from my left rear wheel when I hit the brake pedal. I could hear an impact sound when the brakes engaged, then a scraping sound until I released the brake pedal. If I brake hard, the left rear wheel brake will engage normally at first, then engage violently and stop hard. It releases when I release the pedal. Seemed to be getting worse in the few miles as I drove home.

I replaced all pads and rotors in December 2006 and have driven about 5000 miles since with no problems. At that time I replaced all brake lines with new SS lines, except the left rear hose (above the trailing arm) going to the problem caliper, which had a stripped fastener.

Could this be a:

1. Stuck caliper?
2. Clogged brake line--the one I didn't replace?
3. Something else (e.g. ABS malfunction)?