Whistling noise coming from front left wheel
2001 SL2; 62000 miles
Lately, at random times when the car is going 34-40mph, there starts a whistling noise that seems to be coming from the front-left wheel. My wife described is as a tea pot that starts boiling and, when I heard it myself recently, I have to agree: that's pretty much what is sounds like. Strangely, when the brakes are applied, especially to the point of bringing the car to a stop, the noise goes away. On restart (e.g., light turns green), the noise sometimes starts up again right away; sometimes it waits until the car gets to 30-40mph. Again, applying brakes seems to kill the sound, if temporarily.
When the sound is happening, and the accelerator is released and the car slows on its own, the "whistle" pitch decreases slightly. I say this to point out that the sound is closely tied to the wheel rpm.
As a mechanic myself, I've never herd brake going south making this noise, nor a wheel bearing. The usual wasted-pad sound is a metal-on-metal grinding. Most failed bearings go thump/thump/thump (though I have heard electric motor bearings give a sort of whistling sound when the bearings go).
I pulled the drivers side wheel and the rotor doesn't look too bad. There's definitely pad on the outside; the inside appears to be pretty worn.
So, any thoughts on what could be causing the whistling tea pot sound?
Does anyone have the thickness tolerance for the rotor thickness?