Loud Squeel Noise Under Dash

[Rick S]

I have a 2001 F350 Super Crew Long Bed With the 7.3 Power Stroke Diesel. Recently while towing my 5th wheel trailer I started getting this loud squeel noise from under the dash when I reach around 65 MPH. At first I thought that it was feedback through the radio, but I disconnected the radio and I still get this noise. Some times it's louder than others but almost always it's there.

 

[Tail_Gunner]

Vacume leak/whistle from the HVAC?
Blower fan motor going bad?


It can't be the speedometer, it's electronic, no old style speedometer cable.

 

[Rick S]

Squeal Noise

I wish it were that easy, this noise is loud and if I slow down to 62 or less it goes away. Really sounds like feed back through speaker accept that it in the dash somewhere.
By the way I was a B-52/KC 135 Crew Chief for 16 years "D-G" models.

 

[Tail_Gunner]

Does it happen all the time or just when you've got the 5'er in trail?

 

[roosterdiesel]

this noise is loud and if I slow down to 62 or less it goes away.

Welcome to SDD!


Could it be a boost leak? Do you have gauges? ANy performance loss?

Once when I left the orange boots on the plenums completely loose they would sound like a high pitched squeal at high boost levels. Didn't do it at low boost levels.

 

[Rick S]

I haven't tried to see if it does it without trailer in tow. I'll check it and see.

 

[Rick S]

I checked and this happens even when not towing my trailer. I don't notice any performance issues, just this loud squeal??

 

[Tail_Gunner]

Does the squeel just start at a certain MPH? Or does it vary depending on if you have a headwind or tailwind?

Does it vary at all with vehicle speed or engine rpm, or maybe even transmission gear?

For the most part, I'm thinking air or vacume leak.

 

[Rick S]

This starts happening at 62 mph and gets louder the faster I go. It will quit when I get back below 62. It doesn't matter if there is any wind in either direction.

 

[Rex-a-FORD]

Have you added or repositioned anything on the outside of the truck. Maybe change d or added an antenna. Anything that would affect airflow over and around the cab.

If so, you may have created an area where a harmonic could develop and create the noise your hearing. I know ya' said it was coming from under the dash, but vibration noises can be transmitted a long ways in these vehicles.