Why waste brake fluid? When I'm trying to diagnose a problem such as this, I adapt an air hose and a blow gun to the brake lines, and operate the brakes with compressed air instead of fluid. It's cleaner and more convenient, and once the brakes are functioning on air pressure, I reconnect the lines, fill the master cylinder with clean fluid, and bleed the system. I leaned that trick when we were fabricating disc brake systems for race cars, using air pressure to clamp the calipers to the rotors while we built custom caliper brackets.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!