Whistling sound from dash

#1

Hi–I have a 89 Ford Bronco XLT 5.8/351. 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 or when I accelerate. It gets loud when I am idling or when I de-accelerate. It is driving normal otherwise–any ideas? Doing some research points to a vacuum leak or brake booster. I had the brake booster replaced 6 weeks ago. About 4 weeks ago, my mechanic replaced 2 fuel injectors, cleaned the remaining 6 injectors and all 8 cylinders. At that time, he also checked for vacuum leaks (there were none) and basically gave it a good once over. Again, it is driving fine at this point, but the sound just started. Thanks in advance for any advice.

#2

Sure sounds like a vacuum leak to me. The center-to-right side of the dash is typically where the heat/AC plenum box with all its associated vacuum lines are located. Maybe, just maybe, the probing by the mechanic may have loosened or cracked a line. Plan on poking your head under the dash to listen for the source.