roaring noise under the hood

I have a 1996 ford explorer 4-wheel drive. When it is cold outside it makes a loud noise under the hood. when you push on the gas the noise will quit. I've took it to the garage but no luck. all he said is it's not in the motor so you can drive it. I need some help with this problem.

What type of noise is it? A clicking or a loud idle? Just curious.....

Might be the fan clutch.

Sounds like the fan clutch. As long as it goes away in a few seconds it is probably be working properly.

I agree with mole. Colder start takes up more energy. My explorer did the same in cold weather here in Canada. Not to worry I say.

m f