t initially used the alloy cylinder block of the TU3 with stronger wet liners. This was thus called TUD3. This engine was particularly prone to early head gasket failure. In the early Citroën AX14D a few engines were needing gasket replacement before the first service. Most TUD3 engines required attention at some point. Built from 1988 until 1994, it was replaced by the larger, iron-block TUD5 in which these issues were resolved.