You said you can hear a metal to metal sound before stopping....
This is exactly what happened to me. Turned out to be the front flex disc. Changed it, now no more metal to metal sound. Have it checked!
1989 300E ("E 300"-Badged)
Monotoned Astral Silver w/ rear lid deck panel
97 Style Replica E420 Rims 205/55/16
Black Grille Insert
Chrome Exhaust Tips
Pioneer Sound system w/ Sub-enclosure and CD-changer