I'd have to see that fluid flow to make a diagnosis. If you only get fluid with the hose disconnected, I suspect that fluid is just running out of the line as air goes in.
A failure to get fluid flow is a common problem on GM front-wheel-drive vehicles. There is a valve in the master cylinder that trips when unequal pressures build up in the two parts of the hydraulic system. That stops the loss of fluid when there's a leak, but it will also trip for other reasons. In this case, the valve likely tripped because of the new caliper. The piston in it has to be run out until the pads contact the rotor. That is the self-adjusting feature of all disc brakes.
This vehicle will have a split-diagonal system that puts the left front and right rear wheels on the same circuit. When pumping the brake pedal to run the piston out, no fluid pressure will build up in that part of the system, and that's when the valve will trip. From that point on, no more fluid will flow from the master cylinder to those two wheels. This can be avoided by never pushing the brake pedal past half way to the floor. Professionals never push the pedal over half way on any vehicle more than about a year old to prevent causing damage to the master cylinder. Given the age of your vehicle, this is another problem you might still run into. Crud and corrosion build up in the lower halves of the bores where the pistons don't normally travel. Pushing the pedal over half way runs the rubber lip seals over that crud and can rip them. That results in a slowly-sinking brake pedal, and that often doesn't show up until two or three days later.
The only way I have ever found to reset the valve in the master cylinder is to loosen the cap on the reservoir, open the bleeder screw on only one of the wheels that isn't flowing any fluid, then give it a quick, short burst of compressed air. It just takes a fraction of a second to reset the valve. You want to avoid sending air into the line any further than necessary. That just makes it harder to bleed.
Once the valve is reset, just let the caliper gravity-bleed. It will only take a minute or two. Once the fluid is flowing, close the bleeder, then pump the pedal half way to the floor repeatedly until the piston works its way out of the caliper and pedal pressure builds up. If the piston is already out, just "irritate" the brake pedal by hand a couple of times, then open the bleeder screw once more to burp out the last few little bubbles that got pushed into the caliper.
Friday, April 14th, 2017 AT 9:39 PM