I changed the pads on my car, and the rear calipers wouldn compress, so I opened the bleeder valve, so I could compress the calipers. Do I need to bleed/flush the brake system now?
I would like to add that the fact you had to open the bleeder to compress the caliper piston may mean you have a problem. When compressing a caliper piston you are in effect pushing the brake fluid behind it back up to the master cylinder, through your hoses, and lines. When a caliper piston cannot be compressed its usually a sign that there is a blockage / restriction in one of those hoses or lines, that lead to the master cylinder. If it was just one of the rear calipers, especially if the pads on that side were worn a lot more than the opposite side, that is probably true, if it was both, then most likely not. Also as far as your question goes, it all depends on how you did the process. There is only one way to be sure, push the pedal, and see if it goes to the floor. If it goes to the floor they need to be bled.
