Brake Master Cylinder problems of the 2011 Nissan Frontier

While driving and attempting to stop at a stop sign the brakes became spongy (not firm) and pedal traveled to the floor resulting in longer braking distances unless I pump the pedal. This occurred after applying the brakes ahead of a stop sign as the vehicle rolled over a bump/irregularity in the road. The abs and vdc (anti-slip) activated briefly then the pedal got soft. It remained in this condition (spongy and excessive pedal travel) until reached my destination. The first instance of this occurring the brake system seemed to correct itself with the vehicle parked and ignition off overnight (good pedal firmness and normal pedal travel and braking distances the next morning). However, after a second time this happened (brake gets soft after abs and anti-slip activates) the spongy and long pedal travel remains. Replaced master cylinder and bled system (used motive power bleeder) did troubleshooting on brake booster, booster vacuum line and check valve and all checked fine. Inspected brake lines for bulges, damage and looseness at all calipers all ok. All pads and rotors checked good (no excessive wear or missing parts). Also, disconnected battery to see if the abs/vdc system resets. No change to brake pedal travel and spongy feel. Brake problems as described still remains.

The brake pedal lost all pressure and brakes did not function properly immediately after hitting some small bump in the road. This caused a collision with the car in front of my vehicle. Even after vehicle was repaired following this collision, master cylinder replacement, and full brake service, this issue still persists. Small road bumps make the brakes momentarily non-functional.

While applying my brakes in traffic while not moving very fast I hit a bump in the road and lost full pressure to my brake pedal it went to the floor and the truck jump to the right hand lane the some thing happened to weeks ago - the master cylinder was replaced at that time - the 1st time the pedal did not come back to full - but on 6/23 after an hour or so the pedal pumped back up (2011 Nissan Frontier).