At some point you pressed the brake pedal too far. That must never be done on any car over about a year old. Crud and corrosion build up in the lower halves of the two bores where the pistons don't normally travel in the master cylinder. When the pedal is pressed more than halfway to the floor, either during bleeding, running the pistons out of the calipers, or when surprised by a sudden leak, the pistons ride over that corrosion and the lip seals can get ripped.
You have an additional problem that only involves GM front-wheel-drive cars. If you look closer, you'll see you are indeed getting brake fluid from one rear wheel and only the opposite front one. When the brake pedal is pushed over halfway, a valve in the master cylinder trips to block one front port and the opposite rear one. A lot of people replace the master cylinder for this, then have the same problem.
The only way I've found to solve this is to close three of the bleeder screws, loosen the cap on the reservoir, open the front bleeder screw on the caliper that is not flowing fluid, then give a quick, short burst of compressed air into that bleeder. Let the fluid gravity-bleed, and gravity-bleed the other three wheels.
If you still need to work the pistons out of the calipers, do that by pumping the brake pedal, but never over halfway to the floor.
Sunday, August 9th, 2015 AT 12:14 AM