We purchased our 2017 Bolt EV in early June 2017 and now have about 5000 miles on it. So far, we've been very pleased with the car. However, a few months ago, the car started to make a rapid tapping sound when the door is opened and the car started. At first, the sound was very intermittent and went away with a brief tap on the brake pedal. Now it's more frequent and some times comes on even while driving, then goes away. I could easily trace the sound to the brake master cylinder. We took the car to a Chevy dealer who confirmed that the sound was not normal. They could not determine what the cause was, so they recorded the sound and contacted GM. The latest from GM is that they will be sending out a part called an "I Brake". Neither the service guy at our local Chevy dealer, nor the certified Bolt technician have heard of such a part, and I couldn't find anything online to identify the part either. If anyone in Boltsville has had a similar issue, or knows what an I Brake is, I would appreciate you sharing this with the group and myself.