Alright guys, what would give off a high pitch faint whistle noise coming from the under the hood on the driverside? It only does it under light throttle, and only when moving between 15-35mph. It does not do it when idling and I can only replicate it while driving, so it wont do it while it is parked and giving it a little gas. Driving down the road or highway at 50-75mph there is no whistle or anything.

Intake is on there tight, that was the first place I checked since we just had it off. the vaccuum lines going to the brake system are fine. Nothing is stuck to the grill or the underside of the truck.

Anywhere else you guys can think of checking???

 

My dads 98 5.9 used to do that and just how you describe it. By chance are you using a CAI?

 

Yes but its not it, mine whistles from it but its not the same whistle noise I have now. I can replicate the CAI's whistle at all speeds and even while its parked. Went over every square inch of it too, pulled it off and put it back on, everything is tight. Its a different whistle than what the intake produces and is coming from the oposite corner from where the CAI is (its on the fron passenger side, this is new one is coming from the driver side).

 

Can you let some one else running the RPMs up with it parked and you look under the hood to try to pinpoint? Would spraying carb cleaner or starter fluid where you think it might be comiing help?

 

Yeah I called up a friend last night to help me pin point it, took him for a drive, he heard it too coming from the drivers side, got out had him raise the idle while I was under the hood trying to hear it and couldn't hear anything. Let him try the same thing and he couldn't hear anything either. It really sounds like a vaccuum leak though.

I dont see why there should be but are there any vaccuum lines going to the transmission? If there are maybe we pulled one loose accidently or something cause thats about the only thing I can think of that was done to it. Nothing else has been done to the truck.

I guess I can also check the exhaust manifolds too, maybe something there got shaken loose, but I dont think it would only whistle in while moving though.

 

Check your drive belt(s) and your pulley bearings. Had the same problem a while back and SWORe it was a vaccuum leak... ended up the bearings in the A/C were worn or something.... replaced the compressor and VOILIA!!!!! IDK, just throwing it out there. Good luck, sh*t like that drives me nuts as well.

 

Sounds like an idler pulley bearing or alternator bearing.