Typical full-lock operating pressures on conventional OEM-style automotive hydraulic-brake systems ... gauge to check pressure at each caliper or drum and at each master-cylinder outlet port.

the bolt is drawn into the cylinder, which locks the arm in place. To make it easy to unlock the arm, a pneumatic solenoid releases the pressure on the system at the touch of a button. The video ...

Did the rear brakes lock up before ... which creates pressure using hydraulic fluid that is directed through high-pressure lines to either a drum wheel cylinder or a disc brake caliper.