My truck just recently started whistling under acceleration. It sounds like a turbo whistle except I dont have a turbo. I have read alot on the alternator whistle but mine is at any temp, hot and cold. Its not very loud, you can definatly hear it though. It increases with rpm just like a turbo whistle and everything. Cant figure it out. I took a piece of pvc pipe I had and listened to all of the pulleys and alternator, cant hear anything that even sounds like a whistle. I have a K&N with gryphon, but have had that for 3 years. Checked out the K&N and everything looks good. Only thing I might do is pull the filter off and see if I can get a change in the whistle sound by moving my hand over the tube opening. I really dont think its the K&N all of the sudden though. I have no clue so any ideas or things to try would be great.
Thanks in advance

2004 5.4 4x4 with 101000 on it replaced all 3 idler pulleys and belt less than 5000 miles ago and the tensioner is on the way

 

It is from the intake plenum. The way it s shaped and the way the air comes through it causes the whistle. I live in ND and all throughout the winter I get the same thing, more in the winter than any other time. A friend of mine here had some engineers from Ford come up and look at it and that is what they came up with.

 

yea with my k&n my truck whistles all the time, its really annoying, you just gotta crank the music and live with it

 

SCBoy, if your whistle is only during cold weather (i.e. 30 degree temps and below), it isn't likely the intake, it's your alternator or idler pulley. It tends to occur in below-freezing temps, but stops after a few minutes once the engine/bearing warms up.

 

The K&N all of the sudden starts whistling? I have had it on for 3 years never heard a whistle. What would make it start to whistle?

 

mine has always whistled, maybe you have a different problem like soonertruck is talking about

 

Mine started to whistle after the tranny was rebuilt. I never had a problem before that work was done and I thought the tranny shop did something that caused it. Mine would do it at different speed just for a second or two unless I could hold the load/rpms right at it. Speeds always varied and didn't make any since to me why it was doing it. It would never do it at idle.

When I say speed varied I mean it would do it at different speeds but not like it followed the speedometer, it would whistle at specific speeds like 18, 28, 32, 38, 42, 44, 46, 61 Those I believe were the speeds that it would do it. And it had to be a light throttle and light load on the engine. Otherwise it was not noticeable

 

My 2006 5.4 has recently started to do the same thing. I took it to the dealership this week and they told me my Roush Air filter need cleaning. So I cleaned it "wasn't dirty at all" and the whistle is still there. makes no sense how it would just start whistling after having it for almost 3 yrs now.

 

My T-Bird does that if I have anything other than a MC air filter in it. In that case I suspect it's the thickness of the lip on the filter + the seal that makes the difference.

 

I have read that a few have changed their throttle body and it started to whistle. Check for a vacuum leak in the intake system, especially with any of the cold air inductions. A loose band could cause, especially in colder climates.

2004 F-150 5.4, Volant cai, 85 mm BBK TB, Twin electric radiator fan kit, underdrive pullys, 200 amp alt., Dynatech 2 into 1 into Banks Monster exhaust, programming and a few other add-ons.

 

Have any of you removed the throttle body and tried to polish the edges of the butterfly or have you replaced the throttle body with a larger unit?

 

The 3V 5.4 is a very musical creature