Brake noise—screeching, squealing, grinding—is one of the most common and obvious warning signs a car gives. Some noises are annoying but low-risk (e.g., dust or glazing); others (metal-on-metal grinding) mean immediate danger and must be fixed right away. Below is a complete, blog-ready guide you can publish as-is: what each noise typically means, likely causes (disc & drum systems), DIY diagnosis steps, shop-level tests, common repairs, urgency, prevention, and a copy-paste note for your mechanic.
Quick summary
- Squeal / screech (high-pitch): often due to pad wear indicator, glazed pads/rotors, light vibration of pads, or contamination (oil/grease).
- Grinding (low-pitch metallic): usually metal-on-metal contact — pads worn to backing plate or a loose/foreign object trapped. Urgent.
- Clicks / rattles when braking: loose hardware, broken anti-rattle clips, or pad movement.
- Judder or pulsation: warped rotors, uneven pad deposits, or ABS activation issues.
How brake systems make noise (short)
When you press the brake pedal, pads press against a rotor (disc) or drum surface to create friction and slow the car. Noise is produced when the normal friction pattern is disrupted — by hard/glazed surfaces, loose components, metal contact, vibration, or contamination. Different noises point to different root causes.
1) Common causes & what each noise usually means
A. High-pitched squeal or screech
Likely causes:
- Wear indicator contact: Many pads have a thin metal tab that contacts the rotor and creates a high-pitched warning when pads are nearly worn out.
- Glazed brake pads or rotors: Overheating (heavy braking) hardens the pad surface and the rotor, causing high-frequency squeal.
- Pad vibration / lack of anti-rattle hardware: Pads can vibrate in their carrier, producing squeal.
- Contamination: Oil, grease, or brake fluid on the pad/rotor causes squeal. Road salt/sea spray + moisture can cause temporary squeal until cleaned.
- Thin or hard aftermarket pads: Some cheap or semi-metallic pads squeal more than OEM organic pads.
- ABS or electronic sensor chirp: In rare cases ABS components or wheel speed sensors can make high-frequency noise.
Typical symptom: high, thin, musical sound when you lightly apply brakes or during initial braking.
B. Metallic grinding (urgent)
Likely causes:
- Pads worn to metal backing plate: The friction material has been used up; metal backing contacts rotor → grinding, sparks, severe rotor damage.
- Loose/foreign object (stone) trapped: Small rocks or debris between pad and rotor can cause grinding.
- Caliper or pad hardware failure causing metal contact.
Typical symptom: loud, harsh, continuous metallic grinding while braking; often accompanied by poor braking feel and possible vibration.
Urgency: Stop driving if grinding is loud/continuous — tow to workshop. Continued driving will ruin rotors and risk brake failure.
C. Pulsation, judder or groan
Likely causes:
- Warped rotors (thickness variation) → pedal pulsation when braking at speed.
- Uneven pad deposit (hot spots) → judder even with new pads/rotors.
- Caliper slide pins sticking → uneven pad wear and pulsation.
- ABS modulation or sensor issues can feel like judder in some conditions.
Symptom: pedal vibration, steering wheel shake, juddering under braking.
D. Rattle or click when braking / over bumps
Likely causes:
- Loose anti-rattle clips / pad hardware
- Loose caliper mounting bolts or broken mounting bracket
- Worn caliper guide pins allowing movement
- Backing plate / dust shield contact with rotor
Symptom: metallic rattle or clicking noise when braking or driving over bumps.
E. Long squeal after braking (hot brake squeal)
- Hot brakes can emit a sustained high-frequency noise for a few seconds after you release the pedal due to thermal resonance of pads/rotor. Usually benign if brief.
2) Disc brakes vs Drum brakes — cause differences
Disc brake specific
- Wear indicator contact, rotor glazing or scoring, caliper piston/pin sticking, pad material deposit, debris trapped, rotor run-out (wobble).
Drum brake specific
- Worn shoe lining rubbing metal, loose return springs or hold-down springs, contaminated linings (oil from wheel cylinder), or warped drum surfaces.
3) DIY diagnostic checklist (safe & low-cost)
Always work on a cool car on level ground. Use jack stands if removing wheels.
- Listen & note conditions: does noise occur on light braking, heavy braking, only at low speed, when hot, or after rain?
- Visual inspection (wheels off preferred):
- Check pad thickness — pad material less than ~3mm → replace.
- Inspect rotor surface for scoring, blueing (overheat), or grooves.
- Look for debris between pad and rotor.
- Check for oil/grease contamination on rotor or pad.
- Check for wear indicator contact: is there a metal tab touching the rotor?
- Spin the wheel by hand: any roughness, scraping or audible noise?
- Check caliper hardware: anti-rattle clips present and intact? Guide pins move freely?
- Check dust shield clearance: bent shield touching rotor can cause squeal/scrape.
- Brake fluid & hoses: leaking fluid or swollen brake hoses can cause uneven pad application.
- If drum brakes: remove drum and inspect shoes, wheel cylinder, springs and drum surface.
- Road test (safe): note speed/temperature when noise occurs; is braking effectiveness reduced?
- Simple temporary cleaning: if contamination suspected, clean rotor with brake cleaner and dry; do NOT use oil. Test again.
4) Shop-level diagnostics & tests mechanics run
- Full road test to reproduce noise under controlled conditions.
- Brake inspection with wheel removal: measure pad thickness, rotor thickness, run-out and thickness variation (micrometer & dial gauge).
- Check rotor surface & hardness: warped or scored rotors.
- Check for metal debris trapped in caliper/pads.
- Measure rotor thickness variation (DTV) — causes judder.
- Inspect caliper piston & guide pins for seizure or sticking.
- Check pad material & manufacturing (OEM vs aftermarket) and seating/bedding condition.
- Check brake mounting bolts torque and anti-rattle hardware.
- Check wheel bearings & hub run-out (bad hub can mimic brake noise).
- ABS sensor and wiring inspection (to rule out sensor chattering).
- Drum brake inspection: check shoe wear, springs and wheel cylinder leaks.
- Brake fluid check (contamination/air) and bleed if needed.
5) Common repairs & typical cost/effort
Minor / quick fixes
- Replace worn pads (and hardware clips).
- Clean rotors and pads (if lightly contaminated) with brake cleaner.
- Reinstall/replace anti-rattle clips or pad shims to stop vibration squeal.
- Bend back dust shield or tighten loose components.
- Lubricate guide pins with proper high-temp brake grease.
Moderate
- Resurface (turn) rotors if within thickness spec and only lightly scored (not recommended if rotors are thin).
- Replace rotors and pads as a pair (best practice).
- Replace caliper slide pins or rebuild caliper.
- Replace drum shoes and hardware.
Major / urgent
- Replace caliper if piston seized and causing inner pad to drag.
- Replace hub / wheel bearing if noise source.
- Replace entire brake assembly if severe rust, deep scoring, or metal-on-metal damage present.
Note on costs: Replacing pads and rotors is common: pads (per axle) and rotors (per side) costs vary by car model and parts quality (OEM vs aftermarket). Caliper replacement is pricier (labour + parts). Always replace hardware/clips when fitting new pads.
6) Urgency & safety guidance
- Squeal alone (wear indicator or glazing): moderate urgency — schedule service soon, but you can usually drive short distances.
- Intermittent squeal after wet driving: often harmless; dry braking a few times usually clears it.
- Light grinding or metal contact: urgent — inspect immediately.
- Loud, continuous grinding or reduced braking performance: stop driving and tow — high risk of rotor destruction and brake failure.
7) Prevention & maintenance tips
- Replace pads before they reach the metal backing — check every service.
- Use quality pads matched to driving style (non-ceramic/organic for quieter operation if preferred).
- Replace rotors when worn beyond manufacturer spec or if DTV is present.
- Replace anti-rattle hardware/clips when changing pads.
- Keep caliper pins clean and lubricated with appropriate high-temp grease.
- Avoid aggressive riding of brake pedal and let brakes cool after heavy use.
- After pad/rotor replacement, follow proper bedding-in (break-in) procedure to avoid glazing and uneven deposits.
- Avoid contaminating pads/rotors with grease or oil (watch wheel bearing work and shops using correct sealants).
- Regularly check dust shields and wheel bearings.
8) How to bed in new pads & rotors (short)
A typical bedding procedure (follow pad manufacturer instructions if provided):
- Perform several gradual stops from ~40–50 km/h to ~10 km/h, avoiding coming to a complete stop.
- Then perform a few firmer stops from ~80→20 km/h to transfer some pad material to the rotor.
- Allow brakes to cool naturally — avoid heavy repeated braking until brakes cool.
Proper bedding reduces squeal and improves performance.
9) What to tell your mechanic (copy-paste)
“My car makes [squeal / screech / grinding / judder / rattle] when I [lightly / firmly] press the brakes.
- It happens (only when wet / cold / after heavy braking / always).
- I noticed [reduced braking feel / vibration / metal flakes / rotor grooves].
- Wheel(s) affected: [front left / front right / rear left / rear right / all].
- Last brake service: [date / km] and any recent work (wheel bearing / hub / caliper).
Please inspect pads, rotors, caliper slide pins, anti-rattle hardware and wheel bearings, and measure rotor run-out/thickness.”
SEO meta & blog extras (copy to paste)
- Meta title: Brake Screeching or Grinding — Causes, Diagnosis & Fixes
- Meta description: Learn why your brakes squeal, screech or grind. Detailed causes for discs and drums, DIY checks, shop diagnostics, common repairs, urgency and prevention tips. Keep your car safe and quiet.
- Suggested keywords: brake squeal causes, grinding brakes, brake judder, worn brake pads, rotor glazing, brake pad wear indicator
Suggested images & captions
- Photo of worn brake pad showing metal backing (Alt: “Worn brake pad metal backing — causes grinding”).
- Image comparison: glazed pad vs new pad (Alt: “Glazed vs new brake pad”).
- Diagram of disc brake assembly highlighting pads, rotor, caliper and wear indicator (Alt: “Disc brake components and common noise sources”).
- Infographic: “5 quick checks when your brakes start squealing” (Alt: “Brake noise quick checklist”).
Quick printable checklist (for glovebox)
- [ ] Note when noise occurs (speed, wet/dry, light/heavy braking).
- [ ] Inspect pad thickness and rotor condition (visual).
- [ ] Check for debris between pad & rotor.
- [ ] Clean rotors with brake cleaner if contaminated (temporary).
- [ ] Replace pads before backing metal contacts rotor.
- [ ] If grinding or reduced braking, stop driving & tow to workshop.
Tiada ulasan:
Catat Ulasan