* Serpentine Belt: This is the most common cause. A worn, cracked, or loose serpentine belt will squeal, especially when the engine is cold or under load (accelerating, turning). Inspect the belt for cracks, fraying, or glazing. Check for proper tension – you should be able to push on it with moderate force, but it shouldn't deflect too easily.
* Belt Tensioner or Idler Pulley: These components keep the serpentine belt properly tensioned. If they're worn or failing, they can cause squealing. Look for signs of wear, damage, or unusual noise from these pulleys when the engine is running.
* Alternator Bearing: A worn bearing in the alternator will often produce a high-pitched squeal.
* Power Steering Pump: A failing power steering pump can make a squealing noise, especially when turning the steering wheel. Check the power steering fluid level.
* Water Pump: Though less common to squeal, a worn water pump bearing can cause noise.
* Accessory Pulley Bearings: Any of the pulleys driven by the serpentine belt (alternator, power steering pump, a/c compressor, etc.) can have worn bearings causing a squeal.
Troubleshooting Steps:
1. Listen Carefully: Try to pinpoint the location of the noise. This will help narrow down the possibilities. Does it change with engine speed or when you turn the steering wheel?
2. Visual Inspection: With the engine OFF and cool, carefully inspect the serpentine belt and all the pulleys and components it drives. Look for cracks, wear, or anything that looks unusual.
3. Check Fluid Levels: Check the power steering fluid level. Low fluid can cause squealing in the power steering pump.
4. Listen While Spraying: While the engine is running and making the noise (be careful!), lightly spray a lubricant (like WD-40) onto the serpentine belt. If the squeal temporarily stops, it strongly suggests a belt or pulley problem. This is a temporary fix only; you still need to replace the faulty component.
5. Professional Help: If you can't identify the problem after these steps, it's best to take your Fiesta to a qualified mechanic. They have the tools and expertise to diagnose the issue accurately and perform the necessary repairs. Ignoring the squealing could lead to more serious problems.
Remember safety first. Always turn the engine off before performing any inspection or repair work. Never put your hands near moving parts while the engine is running.
