Hi
I hear a high pitched whistling sound from the engine compartment when I'm driving and the motor is under load. When I let off the throttle it stops. It is more pronounced when it is cold out. Usually happens going up a hill. I thought maybe my air filter was dirty so I changed it. It didn't solve the problem. Does anybody have an idea of what it might be.

Thanks in advance.

My truck is a 2001 Ford F150 supercab with the 5.4 liter engine.

 

x2. This just started happening to me yesterday on my 4.6

 

Don't be surprised if it's something about your a/c clutch, pulley or compressor or a combo of all three. Mine was doing this years ago, summer it'd go away. Then I got the compressor etc changed, no more noise. I thaught it was pcv, idlers, iac you name it- mind you, the a/c thing might be coincidental but whatever, noise is gone. Just something to keep in mind.

 

It does it even when I don't have the heat turned on. It reacts to throttle input so I was thinking something with the air intake.

 

i have a cai on mine and it does make a noise but nothing like this. I am thinking it is the pulleys or belt or bearings or for some reason even the alt.

 

check your belts & then pulleys/tensioners, etc. that would be my 1st guess to check. good luck guys.

 

Thanks for the help. I will check the belts and pulleys this weekend.

 

Mine stopped. I went for about a 30 min cruise on the higway and it stopped.

 

mine was rattling and made a racing sound and from the inside sounded like a rod knock...turned out to be the original ford 147k mile idler puked...when I took it off it'd clank and grind spinning in my hand freewheel..

 

Mine was doing this last winter for a while when it was really cold. I did some reading here and most people have found it was the alternator. They changed it out and the problem disappeared. It does not hurt anything to leave it alone either. For the amount of time mine does it I just turn the radio up.

 

Still doing it. It changes pitch with the rpms of the engine. Starting to think it might be the alternator. Only does it when the engine is under a load ( going up a hill). I wish it would do it with the truck just sitting there idling. would make it a hell of a lot easier to find out were its coming from.

Might have to get a new CD and use your radio trick.

 

with my P&P i noticed my TB whistles when I get on it (going up a hill). you should open it out and try giving it a shot of TB cleaner

 

Mine did this last year. It turned out to be the belt tensioner. Sucks that I didn't figure it out until I was stranded on the side of the road lol.