2002 T&C 3.3 brakes lowpedal

I have a 2002 T&C. pedal getting spongy, took it to mechanic, verified it was bad mastercyl. replaced with remfg from napa, worked one day, pedal went to floor. remfg cycl had scratches on pushrod. replaced with new factory mastercyl. and resevoir. pedal still seems low. pads all good, no leaks anywhere, he says booster checked out.Still have to pump it once to get better pedal.Any Ideas? 85,000 miles

sounds like there is still air in the system i would rebleed the brakes and if it has drums on the rear i would adjust them up

UPDATE After replacing Master Cyl.and resevoir, found very,very small leak in antilock actuator. MY GARAGE HAD TO GET PART FROM DEALER, HE CHARGED ME $345.For part. 2 hours labor to install. Pedal is good now.
Trying to find out what dealer would chargw for actuator. Thanks,sweenerman