Engine hum/whine, not IAC

[Charlie]

The past few week or so, I've been having the strangest hum coming from my engine. I can't pinpoint the source of the sound, and everything seems to be in order. All I know, is it's not the IAC. It almost sounds like a quiet supercharger, to best describe the sound.

Any ideas on what to check? 4.0 OHV, 173k miles, so I'm worried it might be something major...

There are no differences in how it runs other than the noise, as best I can tell.

 

[88cougar]

I had something similar on my 5.0. Sounded like a worn power steering pump. Turned out to be the idler pulley. Take off the serpentine belt and start the engine. If the sound goes away, spin the pulleys on the idler and the tensioner to see if they are wobbly or make noise. Its a common problem and easy to fix. Use the ford parts to replace the old ones and replace all of them. The Ford parts are more expensive but waaaay better quality than the ones from your local parts store. Hope this helps.

 

[IZwack]

Dunno if you have the stock intake box or like a KKM but check the filter. Clean it or replace it.

 

[JOEZ33]

Mine randomly makes a sound like your describing, and I pinpointed the sound to be coming from the alternator. I think the bearings are starting to wear down and get a little loose. Mine also has 173,000 miles.

 

[73stallion]

i had a mechanic tell me the upper intake gaskets go.