I have a 2001 F-150 SuperCrew that has a "wonderful" whilstling noise at a certain engine loading and when the temps outside are cold...it can happen at 30 or 70mph...so I know it isn't speed related. Usually the noise would go away once the truck warms up, but it is not doing that now. It whistles all the time. Does anyone have an idea what could be causing this?

Thanks in advance for your help.

 

Maybe a cracked, split, or loose Vac hose?

Any intake mods? ..aftermarket intake installed?

 

Check the throttle body. It has holes in it to let air through, they carbon up, get smaller, and start whistling some times.

 

You have what I have, I've narrowed with help from guys here to a tensioner pulley or idler pulley. Makes sense, but originally thaught the torque converter was going. One of these days I will replace both pulleys and see what happens. Of course, I really haven't heard it lately, after a year plus it has silenced, but I know it's there.

 

Interesting problem. I had the same problem on my 98 F150 several months ago. Appeared to come from the serpentine belt area but I never thought of the belt tensioner. It stopped a few months ago and hasn't surfaced since. It would make a loud, whistling sound at idle, but stop when RPMs was increased. Blue, I believe you might have something there.

 

Ya, just going by what another guy recently did to solve, passing the good word through the grapevine.