Hello folks - another odd symptom from my 1998 Ford Explorer, just happened recently. When driving at highway speeds, say about 55mph or more, sometimes, and it's getting more frequent, upon braking, even gently applying brakes very softly to slow down over a long distance, I'm hearing what I would best describe as a whining, high-pitched "turbine-like" sound coming from what I think is either underneath the car or the engine. It sounds like something is spinning at high speed and whining, and as the car slows down , the sound slows down and eventually stops.
Ok, since I am a car dummy, what is going on here? I am suppossedly driving on "Auto" with O/D engaged...but I can't remember hearing this a month ago. Is this something to do with the transmission "bands" or is this a a term from the 1970's. No clue. Car is driveable, but at highway speeds, man, sure hate to brake...getting embarrassing. Anyone, please clue me in if you can. I will take it to a mechanic but kinda wanna know what the problem might be first. Thanks!

 

It sounds to me like either you are past the friction material and are metal on metal, or there is a lot of rust, either on the braking surfaces or just outside the surface, that the friction material is rubbing when you apply the brakes. Either way, a quick inspection by someone familiar with the braking system should help you track down the source. They'll want to remove the wheels so they can get a good look at all braking surfaces as well as the thickness of the pads.

If the noise were due to an ABS sensor not working properly and causing the ABS pump to engage or ABS solenoids to release braking pressure to a one or more wheels, the noise would be at a constant frequency, not changing with vehicle speed so I think you're looking for something mechanical with the brakes. Likewise, the transmission doesn't really care if you're braking so I don't suspect a transmission issue either. If you want to confirm that, try shifting to neutral when coming to a stop. If the noise is still present, the transmission is not the source.

-Rod

 

From your description I would be checking the front pads. They have a metal tab that touches the rotor when the braking material has worn to a thickness requiring replacement...

Do NOT touch the rotor while hot, burns.... Philip