The vibrational predissociation rates of triatomic van der Waals complexes were investigated by a new, computationally simple method. The method is based on three approximations: (a) metastable vibrationally excited states of the complex are described by the vibrational self-consistent field (VSCF) approximation, (b) the coupling among the rotational states of the dissociating diatomic fragment is treated by the infinite order sudden (IOS) approximation, and (c) the vibrational transition that leads to dissociation is treated by the distorted wave Born approximation (DWBA). The predissociation rates, the product rotational state distributions, and the lifetimes of vibrationally excited states of He-ICl and He-I-2 are all computed and are in reasonable agreement with other theoretical and/or experimental results. The suggested VSCF-DWBA-IOS scheme is found to be a very simple but efficient theoretical tool to investigate the dissociation dynamics of van der Waals complexes.