* Belt Material: Not all belts are created equal. A cheap belt might squeal even if new. The material composition affects its grip and ability to transmit power smoothly.
* Glazing: Despite being new, the belt surface might have glazed over. This can happen if the belt is too tight, causing it to overheat and lose its grip. Ironically, too tight is almost as bad as too loose.
* Contaminants: Something like oil, grease, coolant, or even just dust can contaminate the belt's surface, preventing proper grip.
* Alternator Pulley: The pulley itself on the alternator might be damaged, worn, or misaligned. A worn pulley will have a rough surface. A misaligned pulley won't allow the belt to contact it properly.
* Idler Pulley or Tensioner Pulley: Similar to the alternator pulley, these pulleys can also be worn, damaged, or seized. They're crucial for keeping the belt properly tensioned.
* Belt Routing: Is the belt routed correctly around all the pulleys? A misrouted belt can rub against something or not contact the pulleys properly.
* Alternator Bearing: A worn bearing inside the alternator itself can cause the alternator to be slightly out of alignment. This leads to inconsistent belt tension and squealing.
* Water Pump Pulley (Less Likely, but possible): Similar issues to the alternator pulley could apply here too.
Troubleshooting Steps:
1. Check Belt Tension (Again): While you say it's tight, ensure it's not *too* tight. There's usually a specification for belt deflection (how much it bends when pressed). Consult your car's repair manual.
2. Inspect Pulleys: Carefully inspect all pulleys (alternator, idler, tensioner, water pump) for damage, wear, or misalignment. Look for cracks, grooves, or anything out of the ordinary.
3. Clean the Belt: Use a belt dressing (specifically designed for this) or a clean cloth to thoroughly clean the belt's surface of any contaminants.
4. Check for Contamination: Inspect the areas around the pulleys for any oil, grease, or other substances that might have gotten onto the belt.
5. Listen Carefully: Try to pinpoint *where* the squeal is coming from. This can help you isolate the problematic pulley or component.
6. Try a Different Belt (High-Quality): If cleaning and inspection don't resolve the issue, try a different, high-quality belt. This helps rule out a faulty belt as the cause.
If the problem persists after these steps, you likely need a more in-depth inspection by a mechanic. They have the tools and expertise to diagnose and fix more complex issues like a bad alternator bearing or a pulley problem.
