Pontiac Repair: 94 Grand Am brakes, vlave, plastic bracket

Question
My son hooked up a stereo system with a separate power line from the battery to the AMP. The power cable to the AMP rubbed against his air flow replacement for the air cleaner until the plastic coating wore off and caused a power short into the entire car. This heated the brakes lines to the point that the plastic bracket holding the line to the wheel well melted. At the time this happened he had just started leaving a parking lot and his brake pedal went straight to the floor. We have replaced the 2 back brake lines (per ConRad's suggestion) Bleed the ABS system and 3 of the 4 brake lines, the left rear doesn't have fluid coming from it. The brake pedal still goes straight to the floor. I would have expected at least some brake pedal with 3 of the 4 lines clean. Any suggestions on the what to try and replace or check? ConRad's wants about $2,000 to repair and I only paid $1,800 for the car.

Answer
Hi Ken:

Iof this car has ABS that is where the issue is. My guess is the ABS brake valve is bound up with air. The abs unit neds to be bled out. You need a scan tool that has ABS communication abality to command the abs vlave to run and stroke the air out of the unit. If you have fluid out of 3 corners the master cylinder is okay and from the master cylinder it goes into the ABS unit and that is where the problem lies Is my guess. Good luck :)