A: If it was the master, both sides would drag badly. To test, with the car off th ground, apply the brakes till they drag, then loosen 1 bleeder valve. If that 1 side loosens only, it could be the hose internally collapsing (any cracks in it?) If not, the caliper is bad for sure. If both sides come loose, then the master may need changing. Pump the brakes up till they are locking again and loosen the line at the master. If both loosen up, it's master cyl time!
Good test! Would not that also check if the check valves are still installed? Bleeding fluid would release the residual pressure.
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