RESOLUTION:
There was a tiny piece of gravel stuck between the brake rotor and backing plate and that was what was scraping and making the noise. The mechanic explained there are very small cooling air vent slots and that somehow a small bit of gravel had been thrown up such it got through one of those slots and got stuck between the backing plate and brake rotor.
The stone was worn flat on several spots so had been gradually turning and moving and likely would eventually have fallen out on its own. That would explain why the sound tended to come and go some, louder then softer.
I live near a gravel quarry with lots of dump trucks full of gravel driving the local roads, often spilling small amounts of gravel. That’s why I always lag far, far behind those trucks, especially at stop lights because when they start up the trucks often jerk and spill some gravel despite the tarps on top of the load. About a week after the repairs were done I recall driving across a particularly large batch of gravel on one of the streets. It was the next day I began hearing the scraping noise. So, I bet that’s when the bit of stone got stuck in the brake.
The brakes are in excellent shape with surprisingly little wear despite being the originals with 43,000 miles / 6 years on them so as long as they are checked every time the tires are rotated I should be good for many thousands of miles more.
The shop refused to charge me for the 10 minutes it took for them to drive the car, hear the noise, find and remove the stone. They insisted that for regular customer like me they wouldn’t charge for something that minor. I strongly offered to pay but they insisted no.
I did ask what warning tabs would sound like if/when brake pads get thin. The mechanic said it is the same as what I was hearing only typically slightly higher in pitch. He explained that the tabs are made of a fairly brittle metal and can break off once they start wearing, so if I ever again start hearing that sort of high pitched metal on metal sound from a wheel, get the car into the shop without long delay so the brakes can be serviced before the pads are worn through to the rotors.
So, I’m a happy camper! No additional repairs needed, no further ding to the bank account, car is in good shape and I’m good to go into winter weather driving conditions with new tires, new struts, repaired wheel bearing, body dings repaired / rust proofed / repainted. All in all, much to be thankful for.
Thank you everyone for the helpful feedback responses. Your regular efforts on here do help many of us learn how to take better preventive care of our vehicles which keeps us safer and also keep our cars running more miles/years, thereby helping the bank account too. You do a true public service with your time and knowledge shared here on the forum. God bless you for that.
