Struggling to detect a 'ghost' whistling noise coming from under hood-
Only presents itself in cold weather (less than 20F), and under acceleration. As soon as I let off the gas it stops, no matter what speed or road condition. I believe it could be associated with serpentine belt or tensioner pulley wheel or fan ? Unfortunately, it's tough to detect without driving it.

I just replaced tensioner wheel a couple yrs. ago, is it normal for them to wear out soo fast ? Could it be the throttle body?

 

This is common, I reckon - and reports do start being more frequent when colder weather arrives.

Possible sources:

-idler pulleys ( you have two)
-tensioner pulley
-belt
-alternator
-water pump
-air leak around filter drawer ( check the foam seal )
-power steering pump (replace fluid with Amsoil synth ATF)

Process of elimination - low-hanging fruit first.

BTW - as long as the pulleys themselves are healthy, just replace the bearings - much cheaper and very easy to do.

MGD

 

Might check the PCV valve, they can whistle sometimes. If there is condensation plus the cold weather might give you the perfect conditions.

Just a thought.

 

OP doesn't have one, in the traditional sense.

MGD

 

My 1997 4.6 did something similar and it was the IAC valve. I am NOT suggesting this is the problem on your truck, however.

 

Good thang too - OP don't have one o' them niether

BSB

 

EDIT:

Read this - and pause @ Post #72 if you can make it that far

https://www.f150online.com/forums/20...d-weather.html

BSB

 

Not sure if you guys are saying I don't have a IAC or PCV valves on my truck ?
(wondering if I can tackle that issue anyway if it is?)
thanks,

 

No - you don't have either. Not classically.

IAC functions are done programmatically by the ETC / TB assembly & the PCM.

The PCV Orifice is embedded within the valve cover and is non-serviceable. 5.4 3V-specific PCV's are discussed in the looong thread I linked to as well.

As Post #72 suggests, if the symptom disappears as being fully warmed up, it's the alternator. If not, it's anyone's guess, with the intake being included in the list of suspects.

MGD

 

thanks for all of your help and input., much appreciated !!
Being that I have no warranty and it's not a recall item, do you think it's worth taking it in to Ford and pay them to diagnose? or rather just deal with it myself-

 

Pull the serp belt and drive it, see if it goes away. That will help isolate it to a pulley/driven component or something else. You can safely run it for a couple minutes without a belt.

 

So next, I bet you are gonna say the OP doesn't have a Truck either!