Just bought an 08 f150 XL 5 speed that makes this terrible whine sound when idling and in lower 3 gears. My neighbor a small engine mechanic says its the power steering pump but I beg to differ. After doing some research online myself I diagnosed the sound coming from the idler pulley, possibly a worn bearing. The power steering reservoir and surrounding area was covered in muck which supported my neighbors theory. I am led to believe it was taken to a shop and was diagnosed as the power steering and was made a mess of by pouring fluid into the reservoir and pulling apart hoses around the area causing the build up. The sound is constant and doesnt increase or change when turning the wheel only during acceleration. I cleaned up the area and refilled the reservoir and have yet to have the level drop even the slightest with no sign of leaks. When amplifying the whine it seems to be coming directly from the idler pulley despite the opinion of others around me. I am planning to replace the bearing and see where it goes from there. I know these models are notorious for pulley issues and hope to support the theory with my diagnoses, stay tuned..

 

Easiest thing to do, take the belt off.... and spin the pulley by hand. You should here a noise if it's going bad. No sense in just throwing parts at it lol it's easy enough to diagnose

 

If it's the idler pulley, you will hear it at all rpm. When mine was going bad, the sound became more high pitched the higher the rpm

 

Idler pulleys are cheap; replace them regardless.

 

How can we diagnose your problem over the internet? You have someone mechanically inclined there to hear and see your problem. Now you didn't like his answer, so just go do what you wanted to do in the first place.

 

Yeah...

 

Buy an automotive stethoscope or use a long handled screwdriver. Careful for the belt

 

Bingo. Pulley's are very cheap and easy to replace. Power steering pumps are expensive and not so easy to replace. Kind of a no brainer here. I replaced mine years ago in the Advance Auto Parts parking lot in 5 minutes. Silent ever since.

 

I hate when people exaggerate ... it's easy but, it takes longer than 5 min.

 

especially removing a belt/re-installing on a hot engine.
Talk about a sweat bath