The parking brake does not use the regular brake's hydraulic system. It is totally mechanical.
The best suspect is the lining rusted off a rear brake shoe and is free to move around. The frame of the shoe will need to move much too far to contact the drum, so it will not allow any pedal pressure to build up. The parking brake moves the same shoes, and with the lining broken free, it also cannot move the shoe far enough to be effective.
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Tuesday, March 16th, 2021 AT 9:58 AM