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 is disposed within the valve housing. The valve includes a diaphragm seated against an inner wall of the valve housing and movable between a first position enabling condensate to flow past the diaphragm and out the condensate outlet to selectively drain condensate from the charge air cooler when the charge air cooler is not in a boosted condition, and a second position preventing condensate flow out the condensate outlet when the charge air cooler is in a boosted condition to thereby isolate the charge air cooler from the atmosphere.