I have a 2015 Explorer 6000 miles and I get a humming noise coming from the defrost vent passenger side when I accelerate 40 mph or higher. When I get behind a semi it stops.

It's the cowl (sp?) on the outside of the front windshield under the wipers. The seal isn't tight enough. There are clips they need to tighten. Mine had the very same issue. Drove me completely insane!

This is happening on my 2016 Limited. I figured out it was the plastic cowl when I used the windshield washer to clean some bugs off, and the buzzing stopped for a few minutes. It also stops when you're behind a large truck. I knew then, it must be the wind coming in at a certain angle causing the vibration. I opened the hood later and tried to tighten the six or eight clips myself, but it didn't work. The clips look like philip's head screws from the top, but they're just clips. I stood there turning a screwdriver for an embarrassing amount of time before I figured that one out.

I have a similar problem, rumbling/humming noise on my 2015 Explorer. It only happens at highway speeds with the fan up high. When I switch to recirculate air it stops. Is this the same problem with the plastic cowl, or something with the blower itself. It seems like the air intake must be involved. Suggestions welcomed!

Well I had a 15,000 mile checkup last week at the dealership, and while there I mentioned the buzzing noise. Told the rep what it sounded like, when it tended to happen, and that I knew it was the cowling just under the hood at the windscreen (even though it was only and educated guess), and was told they'd look into it. Keep in mind, I'm on the Maintenance Plan there. When they called me to say they'd replaced the cowling, free of cost, I was astonished. As far as I am able to tell, it solved the problem. I haven't been over 60 yet, but the buzz usually started at 40 in my case.

Thank you folk, there is the same with my car. It sounds after 45 mph and stops for a minutes after I use the windshields washer (when water is added) and stops after 60 mph. I checked, knock, hold everything, stop the music, the air flow but the sound does not stop. I did not notice what you say about the behind the truck. I'm sure it is the cowl. When I check it I will come back to reflect my experience here.