colt breaker

So, I left my 2015 GT (only 1,500 miles on it) parked on a slight incline at a restaurant, maybe 6"-9" incline over the length of the car. When I was done with lunch (about 45 minutes later), I got back into the car, I pushed the clutch and brake pedals at the same time, and soon as I released the parking brake, the car started rolling backward. The brake pedal felt hard as a rock, and I had to push pretty hard to stop rolling. Once the engine was started, the brakes worked normally. I've never had this problem with any other car, and was able to duplicate it with my Mustang several times. I think my car has a problem with the brake booster loosing vacuum, and wanted to get other owners' info before I head to the dealer. I'm always worried they will say it's normal, even if it's not.

Here are my questions for you...
1.) When you leave your car shut off for more than an hour (maybe even overnight), the first time you push the pedal after that, does it seem hard as a rock, with only an inch or less of movement, or does it go down several inches and make that "shhhh" sound just like it does just right after you shut the car of and push the pedal?

2.) If you park on an incline at night, does your car roll backward when push in the brake and clutch pedal at the same time?

Thanks!

KStev

I Park mine on an incline daily, but usually have the parking brake on until after the engine is started. The one time that I took the brake off to roll the car backwards slightly, I experienced the same thing as you did here. I didn't find any cause for concern with mine since I will not usually do that and figured it was normal with the car since it was not started. Now that I know it happens, I just start it, drift it back quick, then shut it down.