Discovery 2 year 2000 td5 with abs sls etc. After a sequence of very heavy braking, brakes red hot and allmost gone all together, I then lost a firm pedal and whilst it will still stop the car. the pedal under pressure goes slowly to floor .There are no leaks.The old fluid has been completely replaced. Replaced master cylinder, no change. replaced flexi pipes for goodrich ,no change. brakes been bled using two man method and pressure bleeder, no change.There are no abs lights on (and the bulbs are working) Any Ideas greatly appreciated