I definitely hear a hissing sound from the pump ( or so I think it is the pump). Let me describe...There are 3 cylinders connected together and covered by a plastic shroud. One cylinder is bigger than the other two. I figure the bigger cylinder is the pump. Am I correct? What are the other 2 cylinders for? I tried to feel and look which connection the hissing sound is coming from, but could not tell. Any suggestions on how to test or check this out. Would water bubble test work in this case?