So my car has been losing brake fluid for a while. Looked for the leak and could not find. Just kept adding a little. Topped it off couple days ago and kid drove the car and it had almost no pedal. Winter up here so I looked where the car was sitting and saw quite a bit of fluid where the rear tire was sitting. Took off the wheel and could not really see a leak. Ice, snow and sand everywhere. So I cleaned it all up and filled the fluid. Bled brakes at all 4 wheels and can not get any pressure built up at any wheel or get the pedal to firm up. Did the master cylinder loose its prime. I have bled brakes many times and think I know how it is supposed to work.
I would check all your lines since you said you have winter where you live. I am assuming salt is used on the roads. I live in So. CaL but see out of state vehicles all the time with corroded lines that leak with a little pin hole. Also if the vehicle has ABS there is a bleed procedure, and if you cannot find any leak anywhere pull the master cylinder off and look inside the vacuum booster.
There is definitely a leak at the rear wheel and I would say 90% it is the caliper. I cleaned it all up and have it inside so tomorrow I hope to see it dripping, I am just confused why I cannot get the pedal to firm up while bleeding the brakes. Normally when I bleed brakes the air or fluid squirts out. It just dribbles out like no pressure.
You are not going to have good bleed pressure with a leak.
As long as no brake fluid got onto the pads, you should be able to transfer the pads over to the new caliper & continue to bleed the brakes with success.