Newlee, Thanks,
Here is some additional information. When I get my LX570 in for 5K service 10 days ago. I asked the service guy about the noise again. We sit in another LX570 they had in the lot. That one has the same noise coming from the front under the hook. The service guy point out the noise is coming from the brake accumulator. When the brake fluid pressure drop to certain level, the motor will start which make that noise. The motor runs just about every other time when you press the brake pedal. Which confirm this is the nature of LX570. Two days later, when I in a friend’s LX570, it does the same. Both cars make the same noise, just not as noticeable compare to mine.