The pedal drops?? On my accord (very similar to the TL),during hot weather the brake pedal drops a lil bit when the radiator fan shuts off. Maybe this is what you are experiencing, and yes it is NORMAL. However... this could also mean there is air in the brake lines. The next time you go out driving, i suggest turning off the radio and listen carefully to the radiator fan to see when it shuts off and turns on and feel whats going on with the brake pedal.