Was sitting in the car last night with the gf at sonic, had defrosters running and when I was backing out, I heard a loud "PSSSHHHHHHHHHHHHHHHHHHHHHHHHHHH!" Sound like somone slashed a tire. Popped hood, everything was dry.. engine temp was normal, upper and lower radiator hoses tight and pressurized, power steering worked fine..turned on the air conditioning and it never got anything near what it should. I had a new a/c compressor installed recently and had it charged as well. Could something of just let go over time from age?