loud howling noise

[Mr Nelson]

I started the explorer today and had a loud howling noise, it definitely sounded like it came from the front of the engine, I would say it sounded more like a loud supercharger whine. it moved with the rpm then became intermittent and stopped and by the time I went to drive to work and parked it the motor was quiet.

I was thinking maybe a idler pully but could it be the dreaded water pump? I see no leaking.

 

[koda2000]

The idle air control valve (IAC) often causes a howling/loud humming noise when it goes bad. You can try removing it and cleaning it with parts cleaner, but I probably wont help. I've had to replace several off them on different Explorers.

 

[Gary Crist]

Mine did it too! But, it was an unlucky black cat.
Took off like a bat outta he..........llo

 

[J_C]

If it doesn't keep doing it long enough to peek under the hood and locate the source, or you still can't, then you can either take the belt off and check all pulleys for excessive wobble or resistance to turning, or wait for it to get bad enough that it does it more consistently and try running the engine for a moment without the belt to see if the noise stops... IF it's a belt driven component.

While the water pump is not fun, look on the bright side. It's not expensive and is within the realm of moderate skill level DIY (don't need to pull the engine like on a 5th gen 3.5L Explorer) However yes, you'd usually see it start weeping coolant when the bearing fails.

 

[rasouth]

I've had a terrible belt squeak/whine that sounded kind of what you described. As I would start the motor the belts would be a little stiff and cause the whining/squeaking noise until they warmed up a bit. Do what J_C suggested to eliminate the belts and pulleys.