Brake Squeak/Squeal/Moan
Brake squeak or squeal may be due to linings that are wet or contaminated with brake fluid, grease, or oil. Glazed linings and rotors with hard spots can also contribute to squeak. Dirt and foreign material embedded in the brake lining will also cause squeak/squeal.
A very loud squeak or squeal is frequently a sign of severely worn brake lining. If the lining has worn through to the brake shoes in spots, metal-to-metal contact occurs. If the condition is allowed to continue, rotors may become so scored that replacement is necessary.
Humid morning conditions can cause moan until brakes heat and become dry.
The front and rear brake pads are equipped with wear indicators. The indicator will produce an audible noise when it contacts the rotor surface.
Pad wear indicators produce a loud squeal noise to alert of worn out linings before metal to metal contact occurs.