Recently purchased a 1997 C230. Have had others (190E and C280). The issue is with the driver's door not locking. I know the door locks operate by vacuum and can hear an air leak that seems to be somewhere around the driver door hinges. All other doors lock and unlock (accept the driver's side passenger lock knob won't go up at times; may be related). After taking the interior door panel off I believe a 1/8" yellow tube is the vacuum line but cannot find where it goes or the leak. Anyone have a diagram, or knows where this line runs?