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Persistent Brake Squeal on 2020 C300 - Driving Me Crazy!

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Heather Y. · rep 0 · May 22, 4:15 AM · 1 replies · solved · Question

Vehicle: 2020 Mercedes-Benz C300

Hi all,

I've got a 2020 Mercedes-Benz C300 and for the past few weeks, I've been experiencing a really annoying, high-pitched squeal every time I apply the brakes, especially at low speeds. It's not just when the brakes are cold; it happens even after driving for a while.

I had the car serviced about 6 months ago, and they said the pads and rotors were fine. Is this normal for Mercedes brakes? It's really embarrassing in traffic. I've tried a few hard stops to 'bed' them in, but it hasn't helped.

Any ideas what could be causing this persistent squeal? Should I be worried about something more serious?

✓ Accepted solution

ClearTheCode Admin

ClearTheCode Team · rep 0 · May 22, 4:15 AM

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ClearTheCode admin answer:

Persistent brake squeal on a 2020 Mercedes-Benz C300 can be frustrating, but it's a common issue with several potential causes, not all of which indicate a serious problem.

  1. Common Causes:

    • Pad Material: Mercedes-Benz often uses performance-oriented brake pads that can be prone to squealing, especially in certain temperatures or humidity levels. This is sometimes considered a characteristic of the pad compound.
    • Dust and Debris: Accumulation of brake dust, dirt, or small stones between the pad and rotor can cause noise.
    • Glazed Pads/Rotors: If the brakes have been subjected to excessive heat, the pad material or rotor surface can become 'glazed,' leading to a hard, shiny surface that squeals.
    • Worn Pads/Rotors: While you mentioned they were fine 6 months ago, continuous use can lead to wear. If pads are very low, the wear indicators can cause a squeal. Uneven rotor wear or 'lip' formation can also contribute.
    • Improper Installation: If pads or rotors were recently replaced, improper installation (e.g., missing anti-squeal shims, incorrect lubrication of contact points) can lead to noise.
    • Rust: Surface rust on rotors, especially after rain or washing, can cause temporary squeal until it's worn off.

  2. When to See a Shop:

    • If it's persistent and loud: While some squeal can be normal, if it's constant and bothersome, it's worth having a professional inspect it.
    • If accompanied by other symptoms: If you notice vibration, a grinding noise, a soft brake pedal, or reduced braking performance along with the squeal, take it to a shop immediately. These could indicate more serious issues like warped rotors, seized calipers, or critically worn pads.
    • Inspection: A technician can remove the wheels, inspect the pads for wear and glazing, check rotors for runout or uneven wear, and ensure all brake components (calipers, pins, shims) are functioning correctly and lubricated properly. They may also suggest chamfering the pads or applying anti-squeal compound.
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