One problem related to brake master cylinder has been reported for the 1999 Buick Lesabre. The most recently reported issues are listed below.
While performing routine maintenance with my son he noticed all the front brake lines were severely rusted and close to failure. This vehicle previously encountered a burst rear brake line on 5-19-09, mileage at that time was 143,304. See NHTSA odi #: 10269462. All metal brake lines from the master cylinder and to/from the abs unit and front wheels were replaced to avoid imminent brake failure. Silently rusting brake lines are a potential for sudden and unexpected brake loss, only giving the driver seconds to react.