Okay so today we where at the dump i left the car running while i was unloading are 1998 ford expedition eddie bauer 4x4 with a 5.4 in it while i would hear a rattle like something was going to fall off about every 45 sec to a min can anyone give me a idea of what it might be has 171075 on it

 

Was the A/C on and perhaps the clutch was cycling on and off?

 

No the ac was not on i know how that sounds and it is alot louder than that.

 

I just experienced the same sort of thing on my 5.4L. In my casenthe serpentine belt tensioner was worn out. if you can catch it doing it, you may see the pulley wheel wobble when the noise happens. It is on the front of the engine kinda passenger side - a pulley wheel on a swing arm.
When I removed the three bolts holding it, I saw the backside. The plastic seal and outer bearing race were gone. Only half of the ball bearings were still there. No lube. Amazing it worked at all. NAPA had the part, and a new belt since the old one had melted against the seized wheel. Ez fix

 

Thanks its dark now will look at it tommarow i thought it maybe was my timing chain i was dreading that i hope that is not the problem.