Hildebrand began his career with Opel in 1980, where he worked on the 1983 Kadett E. In 1986 he joined Volkswagen as Head of Concept Design, overseeing the development of the Golf III.
In 1989 he joined 3M as a design leader and in 1995 returned to the Volkswagen Group to become Alternate Head of Exterior Design at Volkswagen from 1994 to 1998, and in addition Head of Design at the SEAT Centro Tecnico in Martorell, Spain, from 1995 to 1996.