One problem related to engine head gasket leaking has been reported for the 1999 Mercury Sable. The most recently reported issues are listed below.
Vehicle had a massive transmission fluid leak and broke down. Vehicle checked by dealer, who replaced transmission. Two weeks later, leak began again. Vehicle was checked again by dealer ,who determined that gasket was is leaking. Gasket was replaced. Approximately two weeks later, vehicle vehicle had 2 oil leaks.