A vascular jet cooling system for use with a planar power module and a coolant supply includes a manifold housing and one or more jet impingement plates. The manifold housing is constructed of a dielectric polymer molding material, and defines a coolant inlet port configured to fluidly connect to the coolant supply, an internal cavity in fluid communication with the coolant inlet port and containing the power module, and a coolant outlet port in fluid communication with the internal cavity. The jet impingement plate(s) is arranged in the internal cavity. Openings of the plates direct coolant passing through the coolant inlet port onto a respective major surface of the power module. A power module assembly includes a planar power module and the vascular jet cooling system. A method of constructing the power module assembly uses sacrificial materials and overmolding of the jet impingement plates.