My daughter reports the following: Sudden loss of brake pressure, pedal almost to the floor, then to the floor on the next try. This was while driving at slow speed in the neighborhood. She pumped the pedal and pressure was restored. Fluid level was fine, no leaks apparent. I drove it around and it's braking fine for now. When car is in park, motor running, I hear a distinct click when I depress the pedal, and it seems to be coming from shifter area. Any ideas are most welcome. Air in the system that worked itself out? I doubt it's that simple. She's not driving it, of course, until I get to the bottom of this. Thanks folks.

Sedan/auto