Owners of 2013-19 Buick Regal GS models may come into your store with a complaint of a squeak or squeal from the front brakes under light pedal application at speeds below 10 mph.
According to GM, the noise typically occurs after a prolonged soak in high humidity conditions, then tends to dissipate after the brakes are applied a few times at highway speeds. The car maker attributes the noise to the brake pads oscillating in the caliper bracket coupled with moisture infiltrating the pad friction material. Applying a new copper-based brake paste, part #19303310, to the abutment areas of the brake pads where they contact the caliper bracket should eliminate the condition.
Start the fix by removing the front brake pads. Now clean the abutment areas of the pads and caliper brackets with a good brake cleaner. Referencing the illustration, apply the new brake paste to each end of the brake pad backing plate in the areas indicated. Use a good amount of the paste, but make sure it doesn't ooze on to the friction material. To complete the procedure, reinstall the front brake pads, go on the road and check that the noise has been eliminated.