Two problems related to brake disc rotor have been reported for the 1998 Mercury Mystique. The most recently reported issues are listed below.
Warped front brake rotors, causing brakes to vibrate upon application.
When driving at low or high speeds front end shakes. Also, when applying brakes steering wheel shakes excessively, making it hard to control. Dealer says it is brake rotors. Dealer has seen vehicle several times, and can't fix it.