lvacation

Hi guys,


I got my NX300h 1 month ago and just yesterday I noticed a electronic-like hissing sound whenever I press the brake pedals. It disappears whenever I let go of the brake pedals.


It's not exactly a "hiss" but more of a soft high pitch violin-like sound.


Is this normal?
Thank you!

corradoMR2

From past two Lexus hybrid ownership, the sound is the regenerative braking. I believe that short of a video of the sound in case it's something totally different, I'd say it's normal.

lvacation

Thanks for the reply! Does the regenerative braking occur even when I press the brake pedal while the car is in the Parking mode? (I hear the sound while parked in the carpark with the brake pedal pressed)


Haha, it's more of an annoyance cos now that I noticed it, I hear it everytime I press the brakes... but as long as the stereo is on, I don't really hear it! Other then this, I'm loving the NX

corradoMR2

Yes, if I recall, the moment you depress the brake you'll hear a click and a slight hiss but is very faint. Enjoy your MPGs!

legrunt

Most cars have a vacuum powered booster that assist your brakes.
With most non-hybrid cars, this vacuum is supplied by the engine while it is running.
With Toyota/Lexus hybrid cars, the car has the capability to shut off the engine and run on pure battery mode. Therefore, it cannot rely on engine operation to supply the vacuum.

Therefore, there is a small motor/pump that is electrically driven to supply a vacuum when needed. I do believe that is the sound you are hearing. This motor/pump operates even when the car is completely shut down.

Try this. Unlock your car and get in like you normally would, but do not start the car. (when you don't start the car, theres no aircon, radio, just pure silent bliss) Just sit there in silence, and pump the brake pedal a few times. You should hear that faint whirring sound.