ASE G1 Auto Maintenance and Light RepairMaintenance and Light RepairEasy
A client reports a 'grinding' noise when applying the brakes. During inspection, the technician notices deep scoring on the brake rotors and very thin brake pads. What is the MOST likely cause of the grinding noise?
- AOver-torqued lug nuts.
- BAir in the brake lines.
- CA faulty wheel speed sensor.
- DWorn-out brake pads allowing metal-on-metal contact.
Show answer & explanationAnswer & explanation
Correct answer: D. Worn-out brake pads allowing metal-on-metal contact.
Deep scoring on rotors and thin brake pads, combined with a grinding noise, are classic symptoms of brake pads being completely worn down, leading to the metal backing plate of the pad contacting the brake rotor. This metal-on-metal contact creates a distinct grinding sound.
Why the other options are wrong
- A. Over-torqued lug nuts can cause rotor warpage or wheel stud damage, but not a grinding noise specifically when applying the brakes.
- B. Air in the brake lines causes a spongy pedal feel and reduced braking effectiveness, not a grinding noise.
- C. A faulty wheel speed sensor affects ABS operation and stability control, typically causing warning lights and potentially erratic braking, but not a grinding sound from the brakes themselves.
Brake Grinding Noise
A harsh, metal-on-metal sound heard during braking, typically indicating severely worn brake pads allowing the backing plate to contact the rotor.
- Often accompanied by reduced braking performance.
- Requires immediate inspection and replacement of worn components.
- Can lead to rotor damage, requiring resurfacing or replacement.
Memory trick: Brake noises tell a story; grinding means metal is meeting metal.