A purchased my 2000 F150 used with 81k on it. I love the truck but at city speeds, say between 35 - 45, there is a very faint whistling noise. It is real high pitched but low volumn, and seems to come an go based on the speed. At first I thought it was comming from the radio, so I cut it off -- still there. The bast I can narrow it down to is it occurs when I let off of the gas below 45 mph and it also presents when accelerating from 35 - 45. It also seem to be comming from the driver' side. Very strange.

I think it is a vaccum leak, but I'm not sure. Any body have any clues?

Thanks,
Mark

2000 F-150 Ext Cab Lariat, 5.4, 4x4

 

Do you have an aftermarket intake or a billet grill?

 

does it change with fan speed? I mean the blower speed on your heat...? Also if you have the opening window behind the seat then try moving it to the left or right while its whistling...

 

could possibly be a wheel bearing. A high pitch squuek can sound like a whistling sound

 

i have a 91 XLT Lariat, and it whistels really loud and annoying when the rear sliding window comes loose a little, i dont have a lock on it, so it can move from time to time, and all i do is move it and it stops. Hopes that helps, but what the other posts say could very well be true.

 

I've checked everything noted above (except for replaceing the wheel berrings).

I truly believe that it is a vaccum leak - while paying more attention to it, the sound increases with acceleration and deceleration. When I coast and the engine is at idle speed (not pulling and slowing the engine) the sound disappears. It reappears when I begen to accelerate or if the engine is slowing the truck.

AC/Heat is off and all windows are sealed.

This is really befuddling me.

 

Have you tested this while sitting still? Hood up. Set the parking brake, put it in gear and slowly apply the gas. this will simulate a load on the motor as if you were traveling down the road. If it doesn't make the noise sitting still, then it isn't a vacuum problem.

That leaves moving parts and body part alignment. And those are almost impossible to pin-point because you have to be at speed to hear them.

Sorry I can't be of more help.

 

I had close to the same thing and took My Supercrew to Ford as it is still under warranty.

They tell me the whistling which occurs from 1800 to 2200 rpm's is in the cooling system and they will have to install flow restrictors in the thing to correct this problem.

I won't know until next week as to the outcome of this as the parts are on order per the Engineering Dept. at Ford.

 

there is also a TSB on a noise that occurs from the front dif

 

OK, I've done my best to listen more carefully and pay more attention to the occurance of this noise and noticed that it corrlates to the throttle position. It begins at around 40 mph and continutes thru highway speeds. At certain points during acceleration it begins and then once at cruising speed it stops. Then it reoccurs when the engine is slowing the truck - but I can make it stop by lightely pressing the accelerator to the point which the engine is not slowing. It's really baffling me - but I believe it is a vaccum leak. I do not not have a lot of mechanical knowledge where this truck is concerned - by I know basic mechanics. Is there any knid of vaccum that is connected to or controlled by the accelerator?

Thanks for everyone's feedback and suggestions.
Mark