One problem related to engine grinding noise has been reported for the 2007 Dodge Nitro. The most recently reported issues are listed below.
Turned on the a/c today and the worst burning smell came through the air vents. Made my nieces sick. Pulled over and popped the hood and heard metal grinding sound and smelled like something burning. Was told I need a new compressor. This will be the second time in 6 months I'm replacing it.