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Squealing Noise from Engine Bay on 2021 GLE 350 - Serpentine Belt?

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David L. · rep 0 · May 22, 4:18 AM · 1 replies · solved · Question

Vehicle: 2021 Mercedes-Benz GLE 350

Hi everyone,

I've got a 2021 Mercedes-Benz GLE 350 (W167) with about 30,000 miles on it. For the past week or so, I've been hearing a distinct squealing noise coming from the engine bay, especially noticeable on cold starts. It usually lasts for a few minutes and then either goes away or becomes much quieter once the engine warms up. It seems to be coming from the front of the engine.

Could this be the serpentine belt, or maybe an idler pulley? The car is still relatively new, so I'm a bit surprised. Is this something I should be worried about, and is there anything I can visually check myself? No warning lights are on.

✓ Accepted solution

ClearTheCode Admin

ClearTheCode Team · rep 0 · May 22, 4:18 AM

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Hello David,

A squealing noise from the engine bay, particularly on cold starts and diminishing as the engine warms up, is a classic symptom of an issue with the serpentine belt or one of its associated pulleys. While 30,000 miles is relatively low for a belt to fail completely, issues can arise.

Here's what could be happening and what to check:

  1. Serpentine Belt Condition: The belt itself can wear, crack, or glaze over time, especially if exposed to oil or coolant. A glazed belt loses its grip, causing it to slip and squeal. On cold starts, the belt material is stiffer, and accessories like the alternator or power steering pump (if hydraulic) might put more initial load on it.
  2. Tensioner Pulley: The serpentine belt is kept under constant tension by an automatic tensioner. If the tensioner spring weakens or the pulley bearing starts to fail, it won't maintain proper tension, leading to slippage and noise.
  3. Idler Pulleys: Your engine has one or more idler pulleys that guide the serpentine belt. The bearings within these pulleys can wear out, causing a squeal or grinding noise. This is a very common source of belt-related noise.
  4. Accessory Pulleys: Less commonly, the bearings in an accessory like the alternator, A/C compressor, or water pump could be failing, causing resistance and making the belt slip over that pulley.

What you can visually check:

  • Belt Inspection: With the engine off and cold, carefully inspect the serpentine belt for cracks, fraying, glazing (a shiny appearance), or missing ribs. Look for any signs of oil or fluid contamination.
  • Pulley Play: Gently try to wiggle each pulley (tensioner, idler, and accessory pulleys) by hand. There should be no excessive play or wobble. Spin them by hand to listen for grinding or rough bearing noises.

When to See a Shop: If you can't identify the source or if the noise persists/worsens, it's best to have a qualified Mercedes-Benz technician inspect your GLE 350. They can:

  • Pinpoint the Source: Use a stethoscope to accurately identify which pulley or component is making the noise.
  • Replace Components: Replace the faulty belt, tensioner, or idler pulley with genuine Mercedes-Benz parts. It's often recommended to replace the belt and tensioner together if one is failing.

Ignoring a squealing belt can lead to it breaking, which will cause a loss of power steering, charging, and potentially overheating, leaving you stranded.

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