Stuck front pistons/floating caliper or bad brake hoses?
ABS will default simple (ie as it it weren't there), not rock hard and no brakes. It's a servo system that releases the fluid pressure, then re-applies it, no way to give a very hard pedal.
1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!