I have an 08 f150 with the 5.4. Issue sounds like air getting sucked in from engine compartment. Starts about 2800 rpm and just gets louder from there. Not throwing any codes and I don't seem to notice any power loss. Just very annoying. Please help!

 

Usually, that would indicate a vacuum leak. Meaning a line is off, broken or cracked. Any of your AC/Heat controls acting funny, like when you give it gas, and the AC/heater blower changes from blowing air on the floor to the window defroster? Any difference in fuel economy? If it is in the engine compartment, look for any broken or cracked lines. Sometimes a split in the line that runs along it's length can fool you. If you don't see anything, use a spray can of Throttle body/Choke cleaner. Carefully spray around each vacuum line where ever it connects to something If your idle increases or changes that's likely where the leak is at. You can also take a 4'-5' length of small diameter rubber hose and use it like a stethoscope. Put one end at a vacuum line connection and the other end to your ear and listen for any sucking or whistling sound. This is old school and how I use to find suspected leaks in the old days. Of course this is all assuming there is a vacuum leak. Hope you find it....

 

That's not a vacuum leak.

You're just hearing the air going into the intake and there's a resonance at certain RPMs.

 

Thank you for the reply. I do not notice anything with the AC or heat, however I've just noticed over the weekend the truck sort shakes alot in park now. I'm thinking it's related. If it helps, this winter was very harsh and very cold and that's when this started. I will check the lines when I can.

 

If this was the case, then why has it just started doing this over the winter? The truck never made this noise over the past couple years I've owned it.

 

Maybe something (living or dead) got stuck in one of the silencer passages of the intake tube. You could take off your intake tube and shake it around to see if there's anything loose that falls out.

 

That is entirely possible. I have had a snake coiled up on my intake before, and last year my sister was having a problem with her car losing power, bad gas mileage and making strange noises. Sure enough, we took the lid off of her filter housing and a mouse had a big nest in there.

 

This never even crossed my mind. I'm gonna be checking stuff tonight as long as the rain holds off so I'll have a look

 

Update. Just pulled off the intake tube and had some dirt and dust fall out, nothing that should be causing that kind of obstruction. I can't exactly pinpoint where this sound comes from, I may be hearing it from the vents

 

Bump* still need help!

 

If you pulled off your intake tube and "dust fell out" that indicates it is either pulling in air behind the filter somewhere or the filter is deteriorated and letting dust get through.

 

I think we've found the noise is coming from the heater core, I think it clogged up. So now I'm looking to find a good method for an 08 to flush the core and then I'm gonna flush and put new coolant in