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2015 A3 2.0T Squealing Noise & Battery Light - Serpentine Belt/Tensioner?

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Mike T. · rep 0 · May 25, 3:15 AM · 1 replies · solved · Question

Vehicle: 2015 Audi A3 2.0T Quattro

Hey everyone, I'm having a problem with my 2015 Audi A3 2.0T Quattro, which has about 90,000 miles. For the last few weeks, I've been hearing a loud squealing noise from the engine bay, especially on cold starts or when turning the steering wheel at low speeds. It sounds like it's coming from the passenger side.

Yesterday, the battery light flickered on and off a couple of times, and the squealing seems to be getting worse. I popped the hood and saw that the serpentine belt looks a bit cracked and shiny in spots. I'm thinking it's either the belt itself or maybe the tensioner/idler pulley. Could this be causing the battery light too?

Is this a common issue for the 8V A3, and how difficult is it to replace the belt and tensioner as a DIY? What else should I check while I'm in there?

✓ Accepted solution

ClearTheCode Admin

ClearTheCode Team · rep 0 · May 25, 3:15 AM

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ClearTheCode admin answer:

Your symptoms – a loud squealing noise from the engine bay, especially on cold starts or with steering input, combined with a flickering battery light and a visibly worn serpentine belt – are classic signs of a failing serpentine (drive) belt and/or its tensioner/idler pulleys on your 2015 Audi A3 2.0T. This is a very common maintenance item as vehicles approach higher mileage.

Causes of Squealing & Battery Light:

  1. Worn/Cracked Belt: The serpentine belt (also known as the accessory belt) drives accessories like the alternator, power steering pump (if hydraulic), AC compressor, and sometimes the water pump. Over time, the rubber degrades, cracks, and loses its grip, leading to slippage and squealing.
  2. Failing Tensioner: The belt tensioner maintains proper tension on the serpentine belt. If its spring weakens or its bearing fails, it won't keep the belt tight enough, causing slippage and noise. A worn idler pulley bearing can also cause noise.
  3. Alternator Issues (Secondary): A slipping belt means the alternator isn't being driven consistently, leading to intermittent charging issues and triggering the battery light. If the belt completely fails, the alternator stops charging altogether.

Recommended Steps for Diagnosis & Repair:

  1. Visual Inspection: With the engine off, carefully inspect the entire length of the serpentine belt for cracks, fraying, missing ribs, or glazing (shiny spots). Also, check all pulleys (alternator, AC compressor, tensioner, idler) for excessive wobble, play, or signs of grease leakage.
  2. Belt Replacement: This should be your first step. It's a relatively straightforward DIY job for someone with basic mechanical skills. You'll need a serpentine belt tool or a long wrench to release the tensioner.
    • Parts: Use a high-quality OEM or reputable aftermarket belt. Consider replacing the tensioner and idler pulley(s) simultaneously, especially at 90,000 miles, as they are often the root cause of belt issues and are relatively inexpensive compared to the labor involved.
    • Routing Diagram: Take a picture or note the belt routing before removal.
  3. Check for Oil Leaks: Sometimes, oil leaks (e.g., from the front timing cover or valve cover) can drip onto the belt, causing premature wear and slippage. Address any leaks if found.
  4. Monitor After Replacement: After replacing the belt (and tensioner/pulleys), start the engine and listen for any remaining squealing. The battery light should extinguish if the issue was belt-related.

When to See a Shop:

  • If the squealing persists after replacing the belt and tensioner, it could indicate a failing bearing in one of the accessories (alternator, AC compressor, power steering pump).
  • If the battery light remains on or returns after replacement, suggesting an alternator failure or an electrical system issue.
  • If you're uncomfortable with accessing the belt or releasing the tensioner, as it can be tight in some engine bays.
  • If the belt breaks completely, as this will render your car undrivable (no charging, no power steering, no AC).
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