The paper concerns the construction of a compressible liquid-vapor relaxation model which is able to capture the metastable states of the non isothermal van der Waals model as well as saturation states. Starting from the Gibbs formalism, we propose a dynamical system which complies with the second law of thermodynamics. Numerical simulations illustrate the expected behaviour of metastable states: an initial metastable condition submitted to a certain perturbation may stay in the metastable state or reaches a saturation state. The dynamical system is then coupled to the dynamics of the compressible fluid using an Euler set of equations supplemented by convection equations on the fractions of volume, mass and energy of one of the phases.