03 Explorer XLT: Bad master cylinder

[DrRadar]

147k miles. Just replaced all four rotors and pads: One of the front had worn through the pad material and the back of that rotor was gouging. The back pads were still thick -doesn't appear to have lost much/any material since I checked them 55k ago when I last did the front; wrote it off as the back wear more slowly than front.

But the pads looked glazed to me and I was concerned that the rotor was glazed too. Decided to replace rotors and pads...didn't want to wait to have the rotors resurfaced.

But I am concerned the master cylinder is bad because (1) the lack of wear on rear brakes; (2) spongy brake pedal when driving; and (3) the truck seems to "nose dive" when braking.

Is there a way to evaluate the rear brake operation and master cylinder with everything on the car? Or do I need to remove master cylinder to test it? What's best test method?

Thanks for any guidance.

[aleekat]

Before I would remove the master I would do a complete flush/bleed.

[DrRadar]

After changing rotors & pads, I removed as much old fluid from reservoir as I could, filled with new, and started bleeding. Refilled reservoir several times. I can't be certain that I got all the old fluid out, but I got a lot of it.

I failed to mention that when bleeding, the pedal went further down when bleeding the front than the back. I assumed this was normal behavior, but could it be indicative of a failed master cylinder?