Abnormal Noise is Heard from the Engine Compartment when Depressing the Brake Pedal [04/2018 - ]: Description
WARNING: This page is about a different car, the 2022 Toyota Avalon, 2021 Toyota Avalon, 2020 Toyota Avalon, and 2019 Toyota Avalon. However, it is still accessible from the selected car via links, so may be relevant.
Troubleshooting for when abnormal sound occurs from the engine compartment due to air when the brake pedal is depressed.