Abstract: A process for preconditioning assembled parts for leak testing is disclosed. The process includes placing the assembled parts under vacuum to draw out through any unsealed interface of the assembled parts any fluid trapped therein, and while under vacuum, exposing the assembled parts to a liquid conditioning medium (LCM), wherein the LCM may comprise a mixture of water and a low vapor pressure surfactant. The assembled parts exposed to the LCM are then placed under positive pressure greater than ambient pressure to drive the LCM into any unsealed interfaces of the assembled parts. Any residual LCM on the external surfaces of the assembled parts is then removed, and the assembled parts are subsequently tested for LCM ingress.