It is possible that the reservoir was sucked dry the first time I bleeded the rear brakes after installing the new calipers and pads. However since then I have been very carefull to keep the reservoir (I noticed the split compartments early on) topped off while bleeding the brakes. While the engine was runing, 1. my wife would depress and hold the brake pedal, 2. I would loosen the rear bleed nipple - break fluid would squirt and drip out - and then I would tighten the bleed nipple, 3. my wife would then slowly release the brake pedal. This process was repeaded over and over again on the back and front brakes. In comparison the front brake fluid would squirt out with a lot of force and volume while the rear brake fluid would barely squirt out and mostly dribble out. Once the rear brake bleed nipple is tightened the force transfered through the brake fluid to the calipers/pads is insuffient to lock up the tire, to the the extent that I can physically turn the tire by hand (only a little brake pad resistance) while my wife has the brake pedal fully depressed. I am trying to figure out what is wrong here, either I still have air in the brake lines or something else is wrong. The rear brakes were not working when I picked up the vehicle, so I do not know if it had more problems than just the rear calipers and pads. The front brakes appear to work well.