Put car on all four jack stands, jack up the front of the car all the way up higher than the rear. Then bleed the rear should way a good squirt of fluid coming out. If you wanna do it with a vacuum bleeder, attach the vacuum bleeder to the bleeder screw while it’s shut, then pump up to 25 inches and crack open the bleeder screw so you can pull all that air out. If that doesn’t help you need to blow the lines out and master cylinder, then bleed the master cylinder first then the brakes you might have some sediments in the rear lines.
