I just picked up a new (for me) CPO. Love the car. I hear a whine/hum between 15 and 35 mpg when braking or coasting not under acceraltion from the front of the vehicle. The windows need to be up and the fan very low. If I accelerate quickly it is not noticeable. It doesn't make the noise every time I try to recreate it. My wife noticed it the first time she got in the car. I doesn't get louder with more or less speed. There is no vibration through the wheel. If the windows are down it or the radio is on the noise cannot be heard. Any ideas? Thanks.

 

"Front of the car" is a pretty big place. Can you localize it any better than that? Engine compartment / wheels / behind engine compartment / etc.

 

That's the thing, it's hard to pin point. The hum is definitely outside the cabin, if I had to say it's in the engine compartment. It could be wheel bearings, gears or a sound that resonants a due to a vibration when the engine is not driving the wheels. It does not happen all the time. I wonder if it is the start of a wheel bearing problem(40k miles). I had someone listen as I drove by when I heard the hum inside the cabin and they could not hear anything remarkable as I drove by. Please feel free to ask me any more probing questions. I have scheduled a service tech to have a look on 6/8, but I don't want to just rely on the dealer.

 

I think I may have narrow the hum down to the A/C compressor. If I turn it off, the hum ceases. If the A/C is on, the hum sometimes is present.

Could this be a sign that the compressor is starting to fail?

 

My 2002, 3.0 makes the same sound. Goes away with the A/C turned off....

Is this a sign of impending A/C doom?

 

same with my 02 3.0. im new to it though. I was wondering if it was the belts or anything its like a whine clicking noise. But i figured out when im parked and quiet when I turn my AC on that damn thing is loud!.

 

The hum from the 3.0l that goes away with the ac off is the auxillary radiator fan being noisy. As for the original hum, a hum that is hard to duplicate is usually caused by tires. Make sure they arent overinflated. Besides that theres not much you can do. You may want to try swapping tires from front to back and seed if the noise follows the tires.