There is a hissing sound coming from underneath the bonnet

Hi have a problem with my car, temp gauge is fine no overheating, no smoke, no smell no indicator light on car. My car just stalled got heavy and stopped but waited a couple of seconds and was able to drive home. Heard a loud hissing sound coming from a pipe or hose but could not find it. Left it over night and found a puddle of water on the floor. What could this be? Any info is appreciated.