* Worn brake pads' wear indicators: Most brake pads have small metal strips embedded in them. When the pad material wears down to a certain point, these strips contact the rotor, creating a high-pitched squeal. This is a normal warning sign that the pads are nearing the end of their life, even if they aren't *completely* worn out yet.
* Contamination: Grease, oil, or other contaminants on the brake rotor or pad surface can cause squealing. This could be from a brake fluid leak, spilled oil, or even brake cleaner residue improperly cleaned up.
* Glazed brake rotors: Overheating the brakes (e.g., hard braking, frequent downhill driving) can glaze the rotor surface, making it smooth and less effective at gripping the brake pads. This can lead to squealing, vibration, and reduced braking power.
* Rust or corrosion: Rust on the rotor or brake caliper can create uneven contact points between the pads and rotor, causing squealing.
* Loose or damaged brake components: A loose caliper, broken caliper bracket, or a problem with the brake hardware (clips, pins) can lead to uneven pad contact and squealing.
* Brake pad material: Some brake pad materials are simply more prone to squealing than others. This is a more inherent issue and less of a problem that can be fixed easily. Consider switching to a different pad type if replacement is necessary.
* Vibrations: Sometimes, vibrations transmitted through the suspension or other components can resonate with the brake system, leading to noise.
Troubleshooting Steps:
1. Inspect the brake pads: Carefully examine the brake pads for wear. Look for the metal wear indicators mentioned above. Even a small amount of contact with the rotor by these indicators will cause squealing.
2. Inspect the brake rotors: Check for rust, glazing (a shiny, smooth surface), scoring, or deep grooves.
3. Check for contamination: Look for any grease, oil, or other contaminants on the brake rotors, pads, or calipers.
4. Inspect the caliper: Make sure the caliper is properly mounted and moving freely. Check for any signs of damage or rust.
5. Check the brake hardware: Inspect the caliper pins, slides, and clips for wear or damage. Lubricate these components with high-temperature brake caliper grease if needed (follow manufacturer recommendations).
If you're not comfortable inspecting your brakes yourself, it's best to take your Infiniti QX4 to a qualified mechanic for diagnosis and repair. They can pinpoint the exact cause of the squealing and address the issue safely and effectively.
