Weird air noise

Hello all, I have a 2013 Prius hybrid. My rear pads and rotors were making a weird dragging noise. I ruled out everything else and decided to replace the pads and rotors. This car has 203k miles on it. I replaced the pads and rotors on all four wheels and during the process everything went fine except for the right rear caliper piston wouldn’t retract and I had to replace it. I pinched off the brake hose before it meets the banjo and everything seemed to go smooth. I did not bleed the brakes. My brake pedal felt normal after this job, and I went on a couple test drives and it seemed like before but more reactive. As in the brakes feel great. I do not believe I introduced air into the system, but I am not ruling out that possibility. However, now when I push the brake pedal with the car on or off there is this loud noise that sounds like air is dumping out of the car. I couldn’t find a single person talking about this. Is this normal? Is it just the car getting used to the brakes? If anyone could give me insight on this I would greatly appreciate it. Thanks in advance.

 

UPDATE: I ended up bleeding the brakes after those two short test drives, and guess what??? Problem solved. I’m just going to leave this here incase anyone else comes across this issue. ALSO, just wanted to say if you are having issues with the chicken dance and getting into invalid mode, add a little more fluid to your reservoir. I don’t know the why at this time, but it was the only thing that changed and worked after several attempts.

 

Thank you for your answer, I do believe you are correct. I did bleed them and problem solved. Thank you SO much for your reply.