I have a 2012 Ford Escape Limited with 156,000 miles on it. When I rev up the engine or when I'm coasting, it makes this whistling noise. I originally thought it was my AC compressor because it was only doing it when my AC was on, so I replaced it and the pulleys, and it still makes the noise. I took it to a mechanic, and they tried to diagnose it, but they couldn't figure it out, so they told me not to worry about it. It gets worse the longer I drive, but the car runs perfectly fine, and it throws no codes. Should I not worry about it? (putting a link to my Reddit post because it has a video that I cannot attach here)
https://www.reddit.com/r/fordescape/comments/1kj9cl7/whistling_noise_coming_from_car/
I originally thought it was my AC compressor because it was only doing it when my AC was on, so I replaced it and the pulleys, and it still makes the noise.
The AC compressor can of course make noise itself when worn, but even in good condition puts additional load on the entire belt and pulley system. This may cause noise in other components that have worn bearings. (Hopefully the compressor was checked before replacement and not just replaced on a guess.) Bearings in anything else driven by the belt should be checked for wear.
Vacuum leaks can also cause whistling noises so those should be checked for as well.
putting a link to my Reddit post because it has a video that I cannot attach here
There are instructions for pictures and videos in the topic "READ THIS FIRST - Forum Guide" posted near the top of the main page.
