2013 300. Brake pedal is high & normal braking is excellent. Just pulled wheels & lubed caliper slides. Problem: When slowly going up my steep driveway & I stop, the brake pedal appears to have no vacuum & goes down about an inch or so & feels like it's hitting metal. When I take my foot off the pedal, the car is stopped on the hill & after a few seconds, the brakes "release themselves" & the car starts to roll backwards. Besides that, when first driving in the morning, for about the first 1/2 mile, I also have a similar situation where there is low vacuum & inferior stopping ability. After a mile or so of driving, all is fine. Any ideas?