I've got a whine under the hood when I rev the engine a little. It gets louder as the RPMs go up. Don't think it's the power steering or a belt. I think it's coming from the top part of the engine somewhere, but not absolutely sure. I can also hear it from inside the cab, behind the dash. Makes the noise in park if I rev the engine a little or while driving down the road. Sounds like a hiss or a turbo spooling up and quiets down when I'm in OD and the RPMs drop.. I've searched the forums and haven't come up with much. I think I read that someone had an IAC make some kind of noise like this. This is in my '03 250 5.4l XLT. Oh...I also checked tranny fluid and it's at level, red and dose not smell burnt. Any one else had this happen to them or heard of a problem like this?

 

I had a noise like you described and it was the pcv valve.

 

a/c compressor?

 

I would have to say PCV, $3-5 piece at your local auto store. It's on the left valve cover before the oil cap spout...a hose should be connecting to it sitting in a rubber gromet...pull out the PCV and replace it with a new one. I had the same problem and some fte guys helped me out...hope this is useful.

PCV:

 

I replaced the PCV about a month ago and rechecked it. I don't think it's that. I'm going to take me truck somewhere and have them look at it quick. I'll post back when I get it figured out.

 

if it is just in the cold, it could be an Alt. whine, it happens but it is kind of intermittent.

 

If it's a diesel, I had a problem with my EGR cooler leaking and causing my coolant level to drop and I would get a whine the higher the rpms went.

 

If your new PCV is metal, go get the plastic one from the dealership. I had the same thing happen to me and it started when I put the new metal one in. Replaced it with the plastic one and the noise stopped.

 

I did replace it with a metal one. I'll put the old plastic one back on tomorrow morning and see what it does. Man I hope this is the problem.