Ford Expedition whistle sound when braking in reverse?

Thanks in advance for any help.

I recently had my brake pads replaced thinking the whistle sound was coming from worn out pads. Not the case. It mostly happens when I apply pressure to the brakes in reverse gear.

I included a video of the sound. Brake fluid level is fine.

Could it be brake booster? Brakes? Some kind of leak?

No video, no sound.

Take it back brake shop that did the work.

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Thank you, Ill try to send again.

Lets try this.IMG_3561.MOV - Google Drive

I still have the same advice… Take it back where you got the brakes done.

If you just told the shop that did the work…“put new rear brakes on, please” and nothing else, I’d suggest telling the shop you have a noise when you back up and let them do what they trained to do… diagnose car problems.

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Seems most likely a sound like that would either come from the rear brakes or from the booster. Suggest to focus on determining if the sound is coming from the front of the car (where the booster it located), or from the rear, (where the brakes are located).

When the rear pads were replaced, were the rear disc surfaces also cleaned and deglazed? What type of brake pad was used?

Just checked and it’s definitely coming from the front of the car somewheres. Thanks for your time

There’s usually a thick-diameter rubber-looking hose that connects to the brake booster, sourced from the intake manifold. Ask your shop to take a close look at that. Might be cracking, or problem at one end or the other with the connections. Could also be ruptured diaphragm inside brake booster. That’s hidden, not obvious just by looking. Sometimes that will cause brake fluid to get sucked into the engine. Any brake fluid loss? Seeing any unusual looking smoke coming out the exhaust?

Thanks George, will have that checked!