I have owned this van for two months .Since day one, often after start, the brake pedal will travel 80% to the floor (warning light comes on)upon takeoff. It will then do it one more time before it returns to normal for the rest of the drive. Thought this would be an easy fix. I replaced the master cylinder and brake booster. Nothing changed. I replaced the brake proportioning valve and bleed the whole system. No change. This is no signs of fluid leakage (disc front,drums rear) What the hell am I missing??? haha Thanks in advance for any help

 

How is your rear brake adjustment?