Automobile & Light Truck Certification Test A5 BrakesDisc Brake Diagnosis and RepairHard
A technician is diagnosing a vehicle with a loud grinding noise coming from the front brakes during light braking. The noise disappears under heavy braking. Inspection reveals that the brake pads are moderately worn, and the rotors appear smooth with no deep grooves. What is the MOST likely cause of this intermittent grinding noise?
- ALoose caliper mounting bolts.
- BWorn wheel bearings.
- CA severely warped rotor.
- DMissing or improperly installed anti-rattle clips.
Show answer & explanationAnswer & explanation
Correct answer: D. Missing or improperly installed anti-rattle clips.
Anti-rattle clips (also known as pad clips or abutment clips) are designed to keep the brake pads snug in the caliper bracket, preventing them from vibrating or shifting. If these clips are missing or improperly installed, the pads can vibrate and move slightly, especially during light braking, causing a grinding or rattling noise. Under heavy braking, the pads are firmly seated, and the noise typically disappears.
Why the other options are wrong
- A. Loose caliper mounting bolts would cause a clunking noise, especially when changing direction or applying brakes, and would likely lead to severe uneven wear or catastrophic failure.
- B. Worn wheel bearings typically produce a roaring or humming noise that changes with speed, not usually an intermittent grinding specific to light braking.
- C. A severely warped rotor would cause pulsation, not typically an intermittent grinding noise that disappears under heavy braking.
Brake Pad Anti-Rattle Clips
Small metal clips installed in the caliper bracket or on the pads themselves to hold the brake pads securely, prevent vibration, and eliminate noise during braking.
- Prevents pad movement and noise.
- Crucial for quiet brake operation.
- Missing/damaged clips cause rattling or grinding.
Memory trick: Noise means something loose, or rubbing wrong, listen strong.