I am getting a constant chirping or squeeking noise from the front of my 1994 6.5. What does the vacuum pump sound like when it goes out? I recently changed the serpentine belt and found that all other rotators were quiet but the vacuum pump made noise when rotating even slowly. The tension pulley was silent and I don't have an idler pulley so I'm guessing I am on the right track. How much fun is it to change this item?