Cadillac Repair Questions? Ask a Mechanic for Answers ASAP
It must be the master cylinder. I don't believe from what you describe though that that is your problem. Usually when you cannot turn a tire and I assume you do mean spin the tire and not turn the tire, that means the caliper is still applying pressure to the rotor and this is caused by the brake fluid not being able to return to the master cylinder and is caused by the brake hose deteriorated on the inside and clogging up.
Replace the brake hose for each side that is sticking, bleed and you should be fine.