Hi..

I have a 1999 Ford Explorer. I live in Texas which is obviously very warm right now.

I've noticed that when it's really hot outside (late afternoon), my explorer makes a whining/humming type sound when I sitting at a stop light. It doesn't matter if the a/c is on or not. It's a very loud very noticable sound.

As soon as I put my foot on the gas to move again the sound stops..when I get to the next stop light, there is the sound again. It only does it when my foot is not on the gas.

I don't notice this sound in the mornings or late at night after the sun is down. I only get the noise during the hottest part of the day.

Any ideas?

P.S. The radiator and reserve tank have coolant, and I have no check engine light on and all the guages look to be fine. Nothing else abnormal other than the sound. No performance issues of any sort.

Thanks