The statistical and thermodynamic properties of tangent square-well trimers and tetramers have been studied using the Born-Green-Yvon integral equation method. We have calculated the temperature and concentration dependence of the site-site correlation functions over a range of temperatures, and use these results to predict the equation of state. We have made use of our compressibility results in order to map out an approximate spinodal diagram, and have obtained both a binodal and spinodal via the energy route. We discuss our results in the context of simulation data and the predictions of alternative theories.