One problem related to brake fluid leak has been reported for the 2008 Lincoln MKZ. The most recently reported issues are listed below. Please also check out the statistics and reliability analysis of the 2008 Lincoln MKZ based on all problems reported for the 2008 MKZ.
Brakes spontaneously went soft, during travel (30 mph?). Changed master cylinder which seemed to resolve issue. Couple of weeks later, happened again uwhile in motion. Master cylinder changed 2nd time under warranty. Happened third time within weeks traveling about 50 mph. The third time, it happened upon application of brakes (not aggressive) which caused abs activation. Pulse was felt in brake pedal and immediately brakes pedal went soft (almost to floor). Pumping brake pedal firmed the brakes. Couple of days later, tested abs on gravel road by aggressive braking, abs activation and brakes went soft immediately during the action. Pumping up brakes resulted in firming, at top of brake pedal travel without slowing vehicle then into soft travel through 3/4 travel until firmed again at bottom of travel. Concern is that in the event of emergency braking which activates abs, typical braking changes to �soft pedal� (belief of failed brakes) and potential for panic and resulting collision. Dealer tested system today (10/03/2018) and could not diagnose any problem. No dash light was ever activated in any of the events described. No brake fluid leak detected, no loss of brake fluid.