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Help! My 2017 Was Doing This...

25 July 2021
Hello Everyone,
Been a lurker for a while, but I picked up a 2017 Berlina Black with 12k back in May. Absolutely love it. Traded my LC500 (which I also love), and haven't looked back...Until today.

Cruising this afternoon in Quiet mode at about 40mph en route to the gym, which is about a 15 minute drive from my home. I got a call from my wife and muted my blaring music since I didn't have Bluetooth activated. As I'm hearing her ramble about nothing, and the subsequent silence by not having music coming through the ELS, I'm suddenly overwhelmed by a noise that sounded like I was dragging something underneath the rocker panel near the front of the vehicle. I frantically pulled into the nearest parking lot, rolled my windows down, and heard what sounded like metal on metal brakes grinding with a little bit of a belt whine, almost a squeal, emanating from the front lower undercarriage near the front wheels as I came to a slow stop. I got out, looked underneath, and obviously didn't see what could have been causing the issue. I put the vehicle in drive, windows down, and it just sounded awful! A terrible grinding, squealing sound that immediately started as I crawled from 2mph, to 10mph in the parking lot.

Because it had no apparent impact on drivability, I headed to the nearest service road to head back home via the highway, and actually got the vehicle up to about 65 mph, where the issue dissipated greatly. But, it didn't stop completely. I then exited, and started to slow down to around 40mph where the issue resumed as it did when i first noticed it. As I'm cruising, hoping that no one noticed that my $150k Acura was squealing and grinding like a Kia, I drove over some minor road bumps and I SWEAR it sounded like something got knocked back into place, because the grinding and squealing COMPLETELY stopped!! I mean not a peep! I drove around for about 30 more minutes with varying speeds and drive modes trying to duplicate the problem. But, to no avail. I'm soooo sorry for making my first post so long, but does ANYONE have any theories about what that could have been? Was it the suspension? Brakes? Any ideas would be greatly appreciated. A dealer visit is probably in my future, but I'm just trying to determine how quickly i need to get her in by the seriousness of the issue I experienced. Thanks, All!
I would venture that you captured a small rock in the brake system and it rumbled about, until it either broke up or popped out. The brake rotor has a shield that easily amps up the noise. If it were something serious then as you noted it would not just go away. I believe the pads for both the ceramic carbon rotors as well as iron rotors use electronic wear indicators. If they were mechanical as on some cars they would make a squeal type noise that would not go away.
Or you ran over something that knocked a plastic panel out of place. The theory of debris around an axle or brake rotor...yeah thats very possible. I ran over a bag once that melted to my exhaust pipe, its unnerving the first time you have an unknown sound or smell. If your still worried, have it put on a rack with the wheels off and have someone give it a onceover to check bearings, axles, brakes, plastic shards and all. Glad it worked out.