* Radiator Fan: This is the most likely culprit. The fan itself might be failing (worn bearings), the fan clutch might be malfunctioning (causing it to run constantly or at excessively high speeds), or something might be obstructing the fan (like debris or a broken fan shroud). Listen carefully to pinpoint the location of the noise – if it's coming from the front of the radiator, it's almost certainly the radiator fan.
* Engine Cooling Fan Motor: This is a separate motor, and if it's failing, it will make a loud noise.
* Belt Tensioner/Idler Pulley: While less likely to sound *exactly* like a fan, a failing belt tensioner or idler pulley can make a loud whining or squealing noise that could be mistaken for a fan, especially at higher RPMs. Check for squealing or grinding sounds in conjunction with the fan noise.
* Alternator: A failing alternator can also produce a whining sound that might be confused with a fan, especially if it's under load.
* Water Pump: A failing water pump can make a variety of noises, including a whirring or grinding sound, sometimes confused with a fan.
What to do:
1. Safety First: Don't ignore this. A failing fan can lead to overheating, which can cause serious engine damage.
2. Check the Obvious: Carefully inspect the front of your radiator for any debris that might be caught in the fan. If you can safely do so (engine off and cool!), carefully rotate the fan blades by hand to check for smoothness and resistance. Listen for any grinding or unusual noises.
3. Listen Carefully: Try to pinpoint the location and conditions under which the noise occurs (only when the engine is hot, only at high speeds, etc.). This will help narrow down the possibilities.
4. Professional Inspection: If you're not comfortable performing these checks yourself, take your Explorer to a qualified mechanic for diagnosis and repair. This is particularly important if you're unsure about the cause or if the noise is severe. A proper diagnosis will save you time and money in the long run and prevent further damage to your vehicle.
Don't drive the vehicle extensively while it's making this noise, as overheating could result in costly engine repairs.
