A liquid drain valve assembly for a charge air cooler includes a valve housing configured to couple to the charge air cooler, the valve housing having a condensate inlet configured to receive condensate from the charge air cooler, and a condensate outlet, a valve mechanism slidingly disposed within the valve housing and configured to selectively close the condensate inlet and the condensate outlet to facilitate preventing charge air from leaking during condensate draining, and a diaphragm assembly disposed within the valve housing and configured to selectively engage the valve mechanism to selectively open the condensate inlet and the condensate outlet to drain condensate from the charge air cooler when the charge air cooler is in a boosted condition and isolated from the atmosphere.