Did you bleed the brakes till new fluid came out at each caliper? Since you just put new brakes on(rotors,pads etc?) it's always good to flush out the old fluid with new stuff!!
This way you will for sure know you have no air in the lines. My old 300ZX gave me problems once with master cylinder though. Bled all the lines finally at the right rear caliper we got all the air out!!!
