Automobile & Light Truck Certification Test A5 BrakesDisc Brake Diagnosis and RepairMedium
A customer complains of a 'clunking' noise from the front end when applying the brakes, especially when backing up and then moving forward, or vice-versa. The brake pads and rotors were recently replaced. What is the MOST likely cause?
- AWorn wheel bearings.
- BImproperly installed brake pad shims or clips.
- CA faulty ABS wheel speed sensor.
- DInsufficient lubrication of caliper guide pins.
Show answer & explanationAnswer & explanation
Correct answer: B. Improperly installed brake pad shims or clips.
A 'clunking' noise during direction changes under braking often indicates that the brake pads are shifting within the caliper bracket. This is typically caused by missing, incorrectly installed, or damaged shims, anti-rattle clips, or pad abutment clips that are designed to hold the pads snugly in place.
Why the other options are wrong
- A. Worn wheel bearings typically cause a growling or humming noise, not a clunk during direction change braking.
- C. A faulty ABS sensor would affect ABS operation, potentially causing a warning light or erratic braking, but not a mechanical clunking sound.
- D. Insufficient guide pin lubrication would cause drag or uneven wear, not a clunking noise related to direction changes.
Brake Pad Shifting Noise
A mechanical noise (e.g., clunk, click) occurring when brake pads move excessively within the caliper or bracket.
- Often heard during direction changes (forward to reverse).
- Caused by missing or incorrect anti-rattle hardware.
- Can also be due to worn caliper bracket abutments.
Memory trick: Listen closely, the parts speak loudly.