Why Does My Engine Squeal When I Turn It On?

Why Does My Engine Squeal When I Turn It On?

Here’s a typical scenario:

You start your car in the morning, and as soon as the engine fires up, you notice a loud, high-pitched squeal. When you accelerate or make a U-turn, the squealing gets louder and more pronounced.

What’s causing your engine to squeal?  

Although there are a few causes of a squealing engine, one of the most common is a bad or failing serpentine belt. The serpentine belt – or drive belt, as its also known – plays a vital role in the engine. The belt drives many of the engine’s accessories, including the alternator and power steering pump. Therefore, when a serpentine belt goes bad, these accessories stop working.

Think you might have a bad serpentine belt? A telltale sign is that the engine squealing comes from the front of the vehicle and that it persists. Belt squeaking is also especially pronounced when accelerating, on startup, and when making a U-turn. The noise is loud and sounds like a squeal, loud chirp, or squeak.  If your vehicle squeals when braking, on the other hand, that’s most likely a brake issue, rather than a belt.

This article outlines some other problems you might notice if your belt is squeaking and ways to tell if your serpentine belt is failing.


A lousy belt is hard to miss. You’ll notice the high-pitched persistent squealing as soon as you start the engine. And when you accelerate suddenly, the squealing gets worse. On rainy days or during those humid summer days, you notice a greater frequency in the squealing. Unfortunately, a failing belt usually doesn’t turn the check engine light on, and therefore, you’ll want to watch out for the signs and symptoms.

Beyond the high-pitched squeal, a failing or bad serpentine belt also causes other noticeable issues. They include:  

  • Difficult Steering – In many of today’s cars, the serpentine belt drives the power steering pump. If the squealing is more pronounced when turning – for example, when making a U-turn – this may be due to a bad belt. If the belt fails, you will lose power steering, which makes it very difficult to turn the wheel and can be a safety hazard if you’re driving at higher speeds
  • Battery Light – The serpentine belt is also used to drive the alternator, which uses the power generated to charge your battery. Therefore, a failing belt may trigger the low battery light in your car, and when the belt fails, your battery will die more quickly.
  • Overheating – In some cases, the serpentine belt powers the water pump, which plays an essential role in engine cooling. A car that’s running hot may be a sign of a failing belt, and if the belt fails, your vehicle will likely overheat.
  • AC Problems – Your car’s AC system uses the serpentine belt to run smoothly. Therefore, you might notice the chirping starts when you turn the AC on. The squeal will be especially pronounced if you’re accelerating with the AC on.


Today’s cars have strong, durable serpentine belts, and they typically last between 60,000 and 100,000 miles with little required maintenance. Over time, wear and tear can take a toll on the belt and the pulleys, which often results in that high-pitched chirping sounds when you start the car and accelerate.

The most common serpentine belt problems include:

  • Worn/Cracked Serpentine Belt – Serpentine belts have grooves which fit into grooves in the pulleys. Over time, the friction wears down these grooves, resulting in a loose fit. A worn belt can, therefore, begin to slip, which is one of the causes the squeal. Alternatively, cracks can cause the belt to snap.
  • Failing Belt Pulleys – The belt is pulled along by several pulleys. A bad pulley can cause slippage or misalignment. Regular maintenance can detect pulley issues early.
  • Misaligned Belt / Improper Tension – A belt that’s too loose or too tight, or that’s fallen out of alignment, will cause the belt to slip.

Does the Noise Go Away After Warming Up? In cold weather climates, a serpentine belt may squeal on unusually cold days. This is because the belt is stiff and brittle. Often, though, the squealing stops after its had time to warm up. If you notice a squeal that dissipates after warming up and that’s not present on warmer days, the squeal might be weather-related.


When the serpentine belt breaks, the vehicle may become inoperable, which would require an expensive tow and add to the overall repair costs. Plus, since the belt powers the power steering pump, a loss of pressure could result in heavy steering, which presents a safety risk when driving.

That’s why it’s recommended that the serpentine belt is replaced early when the squealing symptoms are first noticed.

Although it may be safe to drive with the squealing for a few days or weeks, the belt will eventually need to be replaced, and for safety, the earlier it’s repaired, the better.


A serpentine belt replacement is a relatively low-cost engine repair. The belts are usually reasonably accessible in the engine, and therefore, they’re easier to replace (e.g., fewer labor costs). Plus, a serpentine belt isn’t a costly part, most price between $30-$80.

Overall, the cost to replace a serpentine belt can vary depending on your vehicle’s make and model. Here’s a quick ballpark estimate of what to expect:

  •    New Serpentine Belt – $30-$80
  •    1 to 1.5 Hours Labor – $100-$200

Therefore, a total replacement cost is usually in the range of $150-$250, although some vehicle makes and models might cost more to replace. This is because some engines have two belts which the additional belt is normally used to drive the a/c compressor. In addition, your vehicle may require a stretch fit belt over a “v” type construction instead of the normal belt tensioner.

Courtesy of hollenshades

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