Hard and high brake pedal

Hi guys. Just picked up a 2004 gt. 41k miles. So it’s been sitting for a while. The brake pedal was rock hard and only moved about 1/2-3/4” then pedal stopped moving. Right front caliper had one seized piston. So replaced that. Pedal a little better. It gets a high and hard pedal under light braking. stops like rotors are faded like rolling stops. It only does it with light braking. Very high hard pedal. Brakes bleed all the way around, fluids good. Replaced both front calipers. Backs went in smoothly.. All calipershad a healthy stream come out when bleeding as well. . I was thinking hydroboost is going. Any ideas? Thanks!!!

Neuron said:

I was thinking maybe pulling off the serpentine belt and seeing if that makes a change in the pedal(if you do it when cold you won't hurt anything for that short period). Brake fluid is hygroscopic and it sounds like moisture got in during sitting, no leaking at the master cylinder?

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I’ll give that a try tom then... no leaks anywhere. Thanks!