Not saying this is the answer...but maybe a possibility...
Some Chrysler PT Cruisers came with rear drum brakes. They would eventually make a noise that sounded like "metal on metal" grinding when applying the brakes. You would swear that the brake shoes were worn out. But when you took the drums off, the drums and shoes looked fine.
If you took a can of brake cleaner, washed away all of the brake dust, and reinstalled the drums...the noise disappeared.
View my fuel log 2015 Mirage ES 1.2 manual: 51.4 mpg (US) ... 21.8 km/L ... 4.6 L/100 km ... 61.7 mpg (Imp)