I know this is not an Explorer forum but i know some models have similar characteristics of others so i am giving this a shot here.

My wives 2003 Explorer has had this issue for several years and seems to be getting worse. I searched the forum for answers and didnt come up with one. I noticed this again while driving on Thanksgiving to her family's house and decided its time to search for an answer.

Here's what's going on: While driving at most any speed, there will be times that there is a loud whistle coming from inside the engine bay and will stop as soon as you give it more gas or let off the gas. You can run 5 miles and it won't happen again, but once it hits its spot, it will do it again. I have looked at the engine and don't see any loose hoses that may cause a vacuum leak. This is an annoying problem because on a 45 min drive it may happen 6-8 times. We can be driving at different speeds and it occurs too. Not just highway speeds of 60+ mph. We have noticed it driving to town at 45 mph too.

Any help on where to look or someone who has had this issue and found the fix?

Thank in advance. I will be driving this next year some once we get her a new one and let my truck rest a little while so I know this will annoy me. She said she just turns up the radio and ignores it. I wish she would tell me what goes on with it from time to time. I don't ride in it or drive it much but when i do i notice the things wrong.

 

I have the same thing going on. I read some where that a guy traced it to his air filter not getting a good seal. I have not tryed to fix it yet cause its only bad on the freeway. I think he said he used to air filter sealant grease.

Hope this helps.

 

My 05 does it also but only on cold mornings. I will add a small bead of dielectric grease in the morning when I can see. Thanks for the tip.

 

UR air filter and tubes to intake for cracks and loose clamps and finally intake gaskets.

 

Replaced my filter yesterday and found the housing was not seated fully. Fixed that issue and no whistle this morning but also only 50 degrees and that was a little warm for mine to whistle. With luck I wont see the cold mornings again to find out if its fixed.

 

I have a 2004 F150 5.4L Triton that would whistle like a tea pot and various speeds and RPMs. Not a whine, grind or growl but a teapot whistle. Drove me nuts looking for a vac leak. The colder it got outside the more the whistle would appear. I had read other forms that indicated to change the alternator. At -24F I finally had enough of the whistle louder than the radio would cover. I changed the alternator 2 days ago. Quiet as a church mouse at low temperatures, RPM's and speeds. I did spin the old alternator and you could hear that the bearings were rough. The Ford window sticker said I had a 130 amp alternator. Good luck finding one. Other threads I read spoke of Ford rating them differently at the time and was actually a 110 amp. My parts supplier only had a 110 amp and that is what I put in.

 

Yup, usually the alternator. I'm changing mine this summer to get rid of the whine.

 

A healthy alternator will even whine when your battery is on its last legs. Before replacing the alternator, swing by a parts store for a free battery load test.

 

If its a loud whistle noise and only cold it is your alt. I have changed quite a few on explorers, expeditions and f150's for this exact concern.

 

What engine is in the explorer? The 4.0 has an IAC valve that makes this noise when it goes bad. $50 and I replaced two. Noise went away both times.

 

the 04-08 MY f150 were known for the factory alt whistle when it gets cold....doesn't really matter on the state of the electrical system...change the alt and whistle goes away...