One problem related to power assist brake has been reported for the 1999 Mercury Villager. The most recently reported issues are listed below.
Sitting at stop sign when loud "pop" occurred-car started rolling; brake pedal went to floor without any result-used parking brake to stop & avoid turning car-released brake to roll out of intersection-again pedal went to floor without result-again used emerg. Brake to stop on side of road-tow operator checked brake fluid level(full) and under car for leaks(none) then pressed brake pedal which went to floor with no results-dealer claims hole in "diaphram" and previous could not happen only power braking out-this is not so there were no brakes power or otherwise working on this car (exception of emerg. Brake.