So my girlfriend has a Jeep Liberty and it makes quite a bit of noise. Most of it coming from squeaky belts. But the other day she told me she started to notice a weird new sound. While idling every 20 seconds or so you can hear a short low pitched squeaky sound that sounds like pressure being released through a cracked gasket or hose or something similar. But with a fairly limited knowledge of engines I have no idea what it could be. Any thoughts?