My 230sl has had a problem of the brakes not releasing after pressing on the pedal even though the pedal appeared, (control rod - no!) to return to normal position. I had to hit the pedal again to get it to release. I replaced the front calipers, flex lines, pads, master cylinder, adjusted rear brakes, and adjusted parking brake, all to no change. Finally after leaving the brakes in the locked position I pulled off the vacuum line off the booster and the brake actuating arm retracted. My problem - brake booster even though it held vacuum. I took it out -easy, 7 bolts total. Carefully moved the master cylinder away w/o removing brake lines. Had it rebuilt by Power Brake Exchange, 260 Phelan Avenue, San Jose, CA 95112, (408) 292-1305, in 2 hours while I waited for 182.00! Brakes work great now.