Whistle sound from dash?

[arizonabronco]

Hi--I have a 89 XLT 5.8/351 and it started whistling today(like a tea kettle) through the dash on the center to passenger side. It lessens/disappears when I depress the brake pedal and when I accelerate and gets loud when I am idling or when I de-accelerate. It is driving normal otherwise--any ideas? Thanks in advance for any advice.

 

[entity-unknown]

It may be something with your stereo. Have you tried driving with your stereo completely shutoff and all your amp(s) off? You can also pull the radio fuse for a minute to see if it still happens.

 

[arizonabronco]

It's probably your speedometer. Either your cable is going bad or the gear to your gauge is bad, but in my experience the cable went bad then the gear went out next. Pull it out and check the end of the speedo cable it should be square, not like a pyramid.

Thanks for the reply--

Are there any other symptoms to look for with the speedometer cable/gear?

I had been doing some searching online, and everything I found pointed to a bad brake booster (which I had replaced about 6 weeks back), but I will look into the speedometer cable. Again, it drives just fine--good electrical, power, runs cold,etc. Thanks again!

 

[arizonabronco]

It may be something with your stereo. Have you tried driving with your stereo completely shutoff and all your amp(s) off? You can also pull the radio fuse for a minute to see if it still happens.

No, my stereo/faceplate was off.

 

[arizonabronco]

***UPDATE with more information*** It started whistling yesterday(like a tea kettle) through the dash. It lessens/disappears ONLY when I accelerate. It does not seem to be affected by braking and, it gets loud when I am idling or when I decelerate. It is driving normal otherwise (oil pressure normal, running cold, starts right up, no rough idle, no hesitation)--any ideas? Doing some research points to a vacuum leak or brake booster. I had the brake booster replaced 6 weeks ago. I lifted the hood, and listened at each footwell inside the truck--can't pinpoint where it's coming from. Again, it is driving fine at this point, but the sound just started. I know I am probably going to have to take it to my mechanic, but I like to have an idea before I take it in. Thanks in advance for any advice.

 

[Seabronc]

You might want to start looking for a broken or disconnected vacuum hose. If you have A/C controls they are operated by vacuum which may explain the difference in pitch associated with acceleration.

Good luck,

>-

 

[miesk5]

and a long shot is this;

Whistle Noise in Air Conditioning System TSB 95-06-15 for 95 by Ford

Source: via thedieselstop.com

wrong year and conditions tho, but Ford at times, issues TSBs for only specific yrs and iggie earlier yrs bec. of the WARRANTY STATUS: Eligible Under The Provisions Of Base Warranty Coverage

one of best diy tools is a vacuum gauge... can help diagnose many problems

 

[Krafty]

it sounds like it could be vacuum, ac pump leak, or anything that would have to build up pressure when not on the throttle, try to check your intake manifold for any seeping air. also check the throttle body, when the throttle plate is closed it builds up vacuum pressure on every part of the air intake system. if fuel injected then the computer may be compensating for the vacuum leak by adjusting fuel - air mixture.

 

[bobstrat]

do you have cruise control? if i remember correctly i think there is a vacuum switch on the brake pedal assembly.