Dipolar excitons in coupled quantum wells (CQW) offer a unique test bed for studying collective effects of an interacting quantum degenerate system. In this work, we study the exciton gas-liquid transition in such a system consisting of GaAs/AlGaAs CQWs. Below a critical temperature, T_C=4.8K, and above a threshold laser power density the system undergoes a phase transition into a liquid state. We determine the density-temperature phase diagram over the temperature range 0.1 – 4.8K. We find that the latent heat increases linearly with temperature at temperatures below 1.1K, similarly to a Bose-Einstein condensate transition, and becomes constant at temperatures higher than 1.1K, up to T_C. Resonant Rayleigh scattering measurements reveal that the disorder in the sample is strongly suppressed and the diffusion coefficient sharply increases with decreasing temperature at T<T_C, allowing the liquid to spread over large distances away from the excitation region. We suggest that our findings are manifestations of a quantum liquid behavior.