I have a 2006 Taurus SEL and lately its been making a popping or rattling noise in the breather box. I've taken the breather off and nothing is in there. Some one suggested it make be the intake gasket but wouldn't I be leaking coolant if that was the case? The car has 87,000 miles and has had regular maint. performed on it.No engine lights are on and the car runs fine. Any ideas?