What frequently happens when fluid isnt annually flushed, rust builds up in the pistons, they sieze, and you have the last caliper not frozen stopping the entire car.
When THAT piston fails, Voila! No more break function.

Replace BOTH front calipers, then all hoses, then flush entire braking system and see what happens.

PS... when the rear resivoir shows low, it is usually dry, and the fluid meniscus looks like it still has fluid.

Terrible design...

Make sure ALL of the reservoir is at the max line, and you are ok...
Low, means empty...

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John HAUL AWAY, OR CRUSHED CARS!!! HELP ME keep the cars out of the crusher! A/C Thread
"as I ride with my a/c on... I have fond memories of sweaty oily saturdays and spewing R12 into the air. THANKS for all you do!

My drivers:
1987 190D 2.5Turbo
1987 560SL convertible
1987 190D 2.5-5SPEED!!!

1987 300TD
2005 Dodge Sprinter 2500 158"WB
1994GMC 2500 6.5Turbo truck... I had to put the ladder somewhere!