On this parts fiche the O-ring, 21.9x2.3 is the most specified component.
The most reasonably priced component used on the Cx400e 1982 (c) E-2 Thermostat-water Pipe is the Bolt,flange,6x25.
This E-2 Thermostat-water Pipe diagram displays the required parts for the Cx400e 1982 (c) E-2 Thermostat-water Pipe.