We address the problem of making nonholonomic vehicles, with second-order dynamics and interconnected over a bidirectional network, converge to a formation centered at a nonprespecified point on the plane with a nonprespecified common orientation. We assume that only the Cartesian position of the center of mass of each vehicle and its orientation are available for measurement, but not the velocities. In addition, we assume that the interconnections are affected by time-varying delays. Our control method consists in designing a set of second-order systems that are interconnected with the robots' dynamics through virtual springs and transmit their own coordinates to achieve consensus. This and the virtual elastic couplings with the vehicles make the latter achieve consensus too. To the best of our knowledge, output-feedback consensus control of underactuated nonholonomic vehicles has been little studied, all the less in the presence of delays.