I just installed a new master cylinder and rear wheel cylinders in my Mazda pickup. The brakes worked awesome for about a day and now the brake pedal goes straight to the floor like there's no fluid in it. I checked the reservoir and it was full. I went to bleed the rear brakes and no fluid came out. This makes me think I have a clogged brake line, but I don't understand why that would make my pedal so squishy.