When a pure 4He droplet is ionized by electron impact, the most abundant fragment detected in mass spectra after ionization is He2 + . All the models that have been proposed thus far to explain the experimental evidence therefore involve the formation of the He2 + molecular ion. The understanding of the interactions between this ion and the surrounding He atoms in the cluster and of their dynamical behavior during cluster break-up is an important element for the modeling of the cluster evolution after the ionization event. In previous works [1,2] we have computed and described the Potential Energy Surface (PES) of the electronic ground state for the He3 + system that provides the required forces between He2 + and He. After ionization He2 + is presumably formed by association of an He + and any of the neutral atoms in the cluster via a 3-body collision process. The ensuing vibrational quenching of the “hot” molecular ion may release the energy necessary to evaporate the entire droplet, or most of it, and give the fragmentation patterns detected by experiments. We present here a model quantum dynamics that generates vibrational deexcitation cross-sections and the corresponding rate coefficients for the collision of He2 + with He. A timescale of the cluster evaporation due to vibrational relaxation is estimated and the present findings are compared with earlier studies on the same system.