Awesome! Thanks for the quick reply jblackburn. Now I am a bit concerned after reading your reply. Mainly because I didn't use to hear it before. I can understand the booster assist providing more vacuum, but if it keeps on doing that till I start the car, I don't think that is expected. I need to check the brake test as you mentioned. The last couple weeks has been in mid three digits here (105 to 112F) but since yesterday we got some heavy rains and temp dropped to high 79F. I wonder if that would affect this any.That noise is a booster pump that builds up vacuum pressure for the brake booster assist when the engine is off
If you hear it pretty often, perhaps you have a bad check valve near the brake booster leaking vacuum pressure and/or a vacuum leak in a hose somewhere. If you ever experience problems with braking in the morning with a cold engine or in reverse, take your car in immediately. Otherwise, I wouldn't worry about hearing the noise too much.
I will do some more data collection on this from today and report back. I sure hope nothing is wrong with my brake system. Gulp! I have wife and two little kiddos with me most long drives everyday.
Thanks again jblackburn!