Whirring sound when on brake

[BoilerTimmay]

Picked up my truck today. It makes a loud whirring sound when on the brake, even when I’m not in gear. Is this normal and I’m sure it has something to do with the regenerative brake system, but can someone explain it?

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[daemonic3]

Oh that's just the dentist in the back seat filling a cavity.

 

[Doublet]

But it seems weird for it to make that sound while stationary.

 

[Orlando150]

Hmmm, I have a Fusion Hybrid and it has an electric vacuum pump that helps to power the brakes when the engine is off (non-hybrids create vacuum from the running engine) that sounds similar. It does make that sound when turning the car on and sometimes when I'm just sitting in it like at a light or in a drive through. But it does not run all the time I have the brakes pressed as you described... just sporadically.

Mine broke at one point and that caused the hybrid system to stop working since it would not be safe without brakes (it ran on gas full time and per the dealer it was safe to drive in this mode). It gave a warning message and I had to take it in to be fixed (free under warranty). I could tell for a few weeks before the sound was different but I didn't realize that it was failing until the message. It's possible yours is failing and needs to be replaced if it is making that sound all the time.

 

[davidh]

I'm considering buying a f150 powerboost but also recall hearing about whirring sounds from the battery (or such) when idle. Is this very annoying and a reason to not buy it?

When I did the test drive, I can't recall the sound happening but maybe I was too excited!

 

[Bryan Simon]

When I did the test drive, I can't recall the sound happening but maybe I was too excited!

That and the Ford guys would not shut up.
This can do this, watch what happens when I push this, Listen to this stereo. etc. etc. non stop for the whole drive.

 

[snoshuu]

That and the Ford guys would not shut up.
This can do this, watch what happens when I push this, Listen to this stereo. etc. etc. non stop for the whole drive.

Typical sales tactic, talk non-stop and play the stereo during the drive to distract their customers victims.
My strategy to counter their tactics has always been to only test the stereo, and other tech while still sitting in the parking lot before driving. Once the actual drive starts, the stereo is immediately turned off so I can hear every noise the vehicle makes or doesn't make. I also ask them to remain quiet so I can hear without distraction, and if I have any questions while driving, I will ask.

 

[05RubiconLJ]

That is a tough one. My Powerboost is on order, so I can't go outside and compare. However, my '96 Cobra would whine like that prior to starting, which was the fuel pump priming. I addition, I have read that the 10-speed's have a trans fluid pump that is not engine dependant. Could be the truck priming the trans for movement. Does this happen at every start or just when the truck sits? Certainly, there has to be a lot of redundant systems on the truck so that everything works correctly, including brakes, with and without the engine.

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