Long time lurker, first time poster. I can usually troubleshoot my pickup issues by searching through the site but this one has me stumped.

Pickup is a 2005 F150, 5.4l, 4x4. No CEL or codes.
On acceleration the pickup makes an annoying whistle/hum sound. The sound began a couple months ago and slowly has gotten louder. I checked and replaced the serp belt, that didn't help so then I removed the throttle body and did a good cleaning. That also didn't help it. Here's an audio file that has the sound, I listened to this and the whistle/hum is louder than what's on the recording.
Let me know if you have any ideas, THANKS!

 

Kinda hard to tell...sounds the whining of a failing bearing....maybe an idler.

 

Check the foam around the air filter box? Doesn't sound like this but it is a common problem that does kind of match what you're describing. Simple to check and fix so it's worth a shot.

 

I put all my chips on this one. Idler pulley or alternator. A mechanics stethoscope (or _long blade_ screw driver to your ear) should narrow it down.

 

Thanks for the quick advice, I'll take a look this evening.

 

I'd go with F150Torqued on a bad alternator. I bought a remanned one from Oreilly and it sounded similar.

 

I removed the serp belt again and the idler pulleys and tensioner didn't spin smoothly. I replaced them and the sound has disappeared.
With the high pitched whine gone, now I'm back to hearing the tick, tick, tick of the cam phasers.

I also checked the airbox and the foam was missing from the filter door. I added some weather stripping as suggested.

Thanks for all your suggestions, I really appreciate it.

 

Glad we could help.

 

tick, tick, tick of the cam phasers. ???


Your description of the sound generally isn't originating from the 'phasers'. But rather the lash adjusters and/or a roller-follower with slack in the roller's needle bearings - OFTEN times near the rear of Bank 1.


Before condemning your phasers to replacement - you might try running some MMO between oil changes and/or pull a valve cover and inspect condition of all roller-followers.


BTW. Thanks for the 'Thanks' acknowledgements too.

 

Could be a tick from exhaust manifold...