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Loud squealing noise from engine bay on 2017 Mazda 6

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Kevin B. · rep 0 · May 22, 4:51 AM · 1 replies · solved · Question

Vehicle: 2017 Mazda 6 Touring

Hello Mazda forum! I'm dealing with a really annoying issue on my 2017 Mazda 6 Touring with about 80,000 miles. For the past few weeks, I've been hearing a loud, high-pitched squealing noise coming from the engine bay, especially when I first start the car in the morning or after it's been sitting for a while.

The noise usually lasts for a minute or two, then either fades away or becomes less noticeable as the engine warms up. It seems to get worse when it's damp or cold outside. I'm pretty sure it's coming from the serpentine belt area, but I'm not 100% certain.

Could this be a worn-out serpentine belt, or maybe a pulley? What should I be looking for, and is this something I can inspect myself before taking it to a mechanic?

✓ Accepted solution

ClearTheCode Admin

ClearTheCode Team · rep 0 · May 22, 4:51 AM

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ClearTheCode admin answer:

The loud, high-pitched squealing noise from your 2017 Mazda 6's engine bay, especially on cold starts and in damp conditions, is a classic symptom of a worn or loose serpentine belt, or a failing accessory pulley. At 80,000 miles, it's a very common maintenance item to address.

Causes of Squealing:

  • Worn Serpentine Belt: The rubber material of the belt can harden, crack, or become glazed over time, losing its grip on the pulleys. This slippage causes the squealing sound.
  • Loose Belt Tension: The automatic belt tensioner might be failing, not providing adequate tension to the belt, leading to slippage.
  • Failing Pulley Bearings: Bearings in one of the accessory pulleys (alternator, AC compressor, power steering pump, idler pulley) can wear out, causing friction and noise. This noise might change with engine RPM or when specific accessories are engaged.

DIY Inspection Steps:

  1. Visual Inspection (Engine Off!): With the engine off and cool, carefully inspect the serpentine belt. Look for:
    • Cracks or fraying along the ribs or edges.
    • Glazing (a shiny, smooth appearance) on the ribbed side.
    • Missing chunks of rubber.
  2. Belt Tension: While difficult to gauge precisely without a tool, a very loose belt might be noticeable. The automatic tensioner should keep it taut.
  3. Pulley Inspection: Gently try to wiggle each pulley (alternator, AC compressor, idler, tensioner). There should be no play. Spin them by hand (engine off!) to listen for grinding or rough sounds, indicating bad bearings.

What to Do:

  • Belt Replacement: If the belt shows signs of wear, replace it. This is a common DIY task, but requires understanding the belt routing and how to release tension from the tensioner. Always use a high-quality OEM or equivalent aftermarket belt.
  • Tensioner/Pulley Replacement: If a pulley bearing is bad or the tensioner isn't providing proper tension, these components will need to be replaced. Sometimes, a new belt alone can temporarily quiet a failing tensioner.

When to See a Shop:

  • If you're uncomfortable working around the engine or releasing belt tension.
  • If, after replacing the belt, the squealing persists, indicating a deeper issue with a pulley or accessory component.
  • If the noise is accompanied by other symptoms like dimming lights (alternator issue) or AC not working (AC compressor issue).
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