* Serpentine Belt: This is the most common cause. A worn, cracked, or glazed serpentine belt will squeal, especially when cold and under initial tension. The squeal usually diminishes as the belt warms up and friction decreases.
* Belt Tensioner: If the belt tensioner pulley is failing, it may not be applying enough tension to the belt, causing squealing. A worn or seized tensioner bearing can also make noise.
* Alternator Pulley: A worn bearing in the alternator pulley can create a squealing noise. This often happens as the alternator spins up.
* Power Steering Pump Pulley: Similar to the alternator pulley, a bad bearing in the power steering pump pulley can also squeal.
* Idler Pulley: An idler pulley provides support for the belt. A bad bearing in the idler pulley will create a squeal.
Less likely, but possible:
* Water Pump: While less common to cause a squeal that goes away, a failing water pump bearing *could* produce a similar sound, especially if it's only slightly damaged.
Troubleshooting Steps:
1. Listen Carefully: Try to pinpoint the location of the squeal. This can help narrow down the culprit.
2. Visual Inspection: With the engine cool, carefully inspect the serpentine belt for cracks, glazing, or fraying. Also, visually inspect all pulleys (alternator, power steering pump, idler, tensioner) for any signs of damage or play in the bearings. Try to wiggle them slightly – excessive movement indicates a worn bearing.
3. Spray Lubricant (Temporary Test ONLY): *Use caution and only as a diagnostic tool.* With the engine running, carefully spray a *small amount* of belt dressing (not WD-40) onto the belt while keeping away from hot components. If the squeal stops temporarily, it strongly suggests a belt or pulley issue. This is NOT a permanent fix and should be followed up immediately with proper repair.
4. Professional Inspection: If you're not comfortable inspecting the components yourself, take your Explorer to a mechanic for a proper diagnosis and repair.
Important Note: Ignoring a squealing belt can lead to serious damage. A broken belt can cause the engine to overheat or stop running completely, leading to significant repair costs. It's best to address the issue promptly.
