VW Jetta Soft/Fading Brake Pedal after working on rear brakes. on 2001 Volkswagen Jetta

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Tried to replace the rear brake pads and wasn't able to due to lack of correct parts and tools. Had to put back together with old parts and use a pair of needle nose pliers to turn in piston. Now the pedal is very very soft and fades all the way to floor consistently. The only time the pedal is firm is with the E-Brake applied or when you slam on brakes. Eben while in park it goes almost to floor. Fluid level is full and never opened any fluid. Thinking either piston was turned in too far and is now seized or air got into system some how.
(1) Answer
Did you adjust the brakes? Once you turn the rear caliper pistons in, you have to "adjust them" using a crazy, but serious technique. Go to an open area (parking lot or empty street) and backup going about 5-7mph. Stomp on the brakes until the car stops. Repeat several times. The rear pistons will reset to the proper position given your current brake pad thickness and your brakes should work better.

If the pedal fades, especially after a stop (car is stopped, pedal is depressed, a few moments later the car rolls or the pedal "gives" more and goes farther in), then your problem could be a bad brake master cylinder.