Yesterday my 07 GT/CS starting making a weiord noise. It sounded like a horn or an alarm.
It seemed to be coming from underneath the car. I disconnected the battery thinking it would stop but it didnt. I began thinking someone rigged a gag device of somekind underneath my car. a quick visual inspection found nothing but the noise stopped after about ten minuites... anyone heard about this or any devices that do this?????

 

had that happen in my truck once. took me 2 days to find it. I thought I was going crazy. turned out to be a kids toy in the console... Ha, Ha

 

Thanks teepee. but i have no kids .... haha.

this is really bugging me. it was a solid steady tone just loud enough to annoy. I could hear it from the living room when the car was in the garage..

 

Pretty tough to diagnose based on what you have described here. I'm assuming the car was running while this noise was going on? Was it constantly making the noise or did it make the noise intermittently and then go away after a few minutes? My it guess is the FEAD idler pulley. There is a TSB out for it. A few winters ago when it got cold my car would make this awful hoot/tone on cold start, and it turned out to be that pulley.

 

Thanks for your info Hypro.... but this is when the car is not running and the battery disconnected... thats why I thinking someone planted something on it,,, and it did it again yesterday. goes for about 10 minutes and stops. Crazy

 

Where underneath is it coming from exactly? It could be pressure bleeding off from the fuel tank, cooling system, etc.