OK, here's the latest scoop. We can't see into the valve hole where the low pressure sensor switch lives but it feels like (using a toothpick) that we do have a valley. Disconnected the two lines out of the master cylinder and the brake pedal goes to the floor and squirts lots of fluid out the hole for front brakes but spits out air and a little fluid for the rear brakes. Does this mean just more bleeding in the rear or a master cylinder repair kit? If it's a repair kit, do we get parts for the main piston, etc. or the trap valve in the banjo fitting? HOPE we are narrowing it down. Many thanks.
Gary and Carla