Magellan55

My car makes a weird buzzing sound for a few seconds every morning as I open the driver door to get in - sounds like some kind of little motor running. I thought it might be the seat or steering wheel, but nothing moves until I sit in it and either power it up or put on the seatbelt. Seems to be coming from behind the dash.

Anyone have any idea what it is? Fuel pump maybe?

HSinNoVa

Don't know what it is, but I hear the same thing when I get in the car also.

tonyscv

It's "normal", but I have no idea why it does it. I assume it's got something to do with engine prep since you would theoretically open the driver door and then start your car shortly thereafter 98% of the time.

lucasb7

It is the brake assist priming itself. When you open the door it builds vacuum pressure so you're ready to stop. You can read more about the technical side of it on PriusChat.

reb737

I have had this noise confirmed by two Lexus dealers as noise coming from the brake booster pump. They say it is "normal." I consider this unsatisfactory and subpar for a Lexus quality auto. I am pushing for a recall on this issue and for Lexus to provide a better pump that doesn't make this noise. You can also hear the noise when you are braking at times.

I test drove a number of Prius and hybrid Camrys before I bought the HS and I did not recall hearing this sound on those vehicles, although I know the HS is using the Camry engine and drivetrain.

YotaCarFan

The noise is normal. An electric pump is used to build up brake fluid pressure and prepare the brakes for use. It occurs when the driver's door is opened so that braking is available immediately when the driver steps in the car, even before the car is started. The pressure stays up for awhile; it is later released if the door is shut and car is not started after a period of time. The Camry and Prius cars you test drove likely had been driven or had their door opened not long before you opened their door, so the pump did not activate in your presence at that time.

A pump is needed because hybrid car engines don't run continuously, making traditional engine vacuum assist a non-option. Making the pump silent would likely be cost prohibitive or it would have been done already. It is actually pretty quiet for a high pressure pump. Contrast its noise level with that of, say, an electric pressure washer, or of the cheap pumps used to spray cleaner on windshields. Also, note that the pump is quieter than the noise of a gasoline engine, which is what provides brake assist in traditional cars.

reb737

Thanks, YotaCarFan, for the details. I am now curious to go check out all the hybrids again and hear their brake booster pump volumes. I suspect that all the Toyota vehicles use the same pump. The Ford Fusion and the new Sonata hybrids would be my next cars to check out to see how quiet a booster pump can get.

ventura12

yeahd
**** wak