Hey. I’m from Los Angeles and our family recently purchased a used BMW 528i (40K miles). Perhaps this is nothing, but I just wanted to make sure anyway.
Today, at around 2AM (maybe 50 degrees C), within minutes of starting the car, we drove into a McDonald’s Drive Thru. While I was ordering and pressing on the brakes, I noticed continuous discharge of white smoke/vapor from the exhaust. For maybe a minute this continued. When I moved the car a little bit to get closer to the window, the smoke stopped. But when I stopped again to receive my order, I saw the white smoke/vapor again. My friends who were with me told me that it might just be water vapor, but the hypochondriac in me wants to make sure this isn’t a blown head gasket or anything else I’ve read about in the internet. BTW When I drove away from the Drive Thru and continued driving, I stopped seeing the white smoke/vapor.
I’m as clueless you can get with cars. Do I need to be worried?
Water vapor is most likely the origin of the smoke. If the trip to McD’s was a short one then you could have been seeing the evaporation of moisture in the exhaust system as “smoke”.
On the other hand if you had been on the xpressway for 40 miles and then stopped at McD’s all the exhaust system moisture would have been burned off by then and the smoke would be a concern.
Monitor the oil level in the motor, and the coolant level in the overflow container. If the fluid levels stay the same for a month or so that would confirm all is OK.
Uncle Turbo is exactly correct, but there is one other long shot possibility. I mention it only because you recently purchased the car so we cannot rule the long shots. You mention that the smoke happens when you press on the brake. Burning brake fluid from a leaking master cylinder makes lots of white smoke. I have seen this happen, but not on a BMW.
I don’t know whether your car has a warning light or a computer read out for low brake fluid, but in case that warning is not working, I would take a look at the brake fluid reservoir while I was checking the water level. On 5 series cars, they have traditionally tucked the master cylinder reservoir under something, so you have to take something off to get to it (not difficult).
Sorry, can’t help the jab…but if it’s 50° C in LA in the middle of the night you’ve got worse problems than smoke coming from a car 
Agree with the others, if it’s only happening within a few minutes of startup on cool days, it’s probably condensation burning off in the exhaust system.
If it’s still producing white smoke after driving it for 15 minutes, then you may have cause for concern. If coolant is getting into the exhaust through a leaky gasket somewhere, white smoke from the tailpipe is a common symptom.
But white smoke upon first starting the engine is normal, especially in cooler weather. It’s just one of the byproducts of combustion, and when the engine parts and exhaust pipe are cooler, the water vapor condenses to form steam, which is the white smoke you see. But that should stop once the car is warmed up, which takes anywhere from 5 to 15 minutes for most cars.
Thanks guys. I have not seen the smoke the rest of today. I guess I worry too much.
“I guess I worry too much.”
On the contrary…credit yourself for paying attention to subtle signs from your car, and for noticing changes in the symptoms relative to moving forward, etc. This attentiveness will serve well later for catching an early sign of trouble before it becomes dangerous or expensive.