Depressurize The Brake System

Fig 1: Bleeding Unit Connected to Brake Fluid Reservoir

Courtesy of VOLVO CARS OF NORTH AMERICA.

Close the cock on the pressure line. Open a nipple and close it again.

Checking for air in the brake system and for brake fluid leakage 

See: CHECKING FOR AIR IN THE BRAKE SYSTEM AND FOR BRAKE FLUID LEAKAGE  .