I have a 1994 Ford F-150. When it is turned upon, it makes a rattling noise that sounds like its coming from the alternator or power steering pump. I'm not sure, since I don't know a whole lot about vehicles. Any suggestions? The rattling starts as soon as the vehicle is turned on, but is very consistent throughout the whole time the vehicle is operating.

 

does it do anything else? vibrate, surge, funny steering, anything like that? if none of these things seem present check and see if the tensioner pully is wore, if it is it wont hold the belt tight.