I just bought a 00 expedition with 40k on the clock and it has the 4.6 in it. Sometimes when I start it and and when sitting in traffic it will make this noise, from the engine, like an air compressor running. It only does it for a few seconds and quits. I tried revving up the motor and that does nothing. Any ideas?

 

It's prolly your cooling fan cycling on and off. it is normal. when you are at speed (above 35mph) your fan is dis-engaged. when you sit at a light depending on how hot your engine is you will hear it engage and diss-engage.

 

It did it this morning when it was -8 when I first started it up. Sounds more like a small gas motor rattle.

 

If you have load leveling, it could be the air compressor running!

 

I have the xlt does it come with that? I guess I'll have to look.

 

good one i didn't even think of the load leveling feature!