how does a pushrod to a brake's master cylinder change position?
 

'92 Honda Accord LX whereby the front brakes aren't releasing properly. I've changed the MC as
it was leaking onto the braker booster outer shell. The brake booster shows no sign of fluid
internally with the MC removed. I have minimal freeplay between the brake pedal & the back of
the pushrod - I move the pedal ~ 3mm before contact with the pushrod. It appears from reading
tegger's info I may need to adjust the pushrod - how could it suddenly change when it is locked
in place and been functioning properly for years?

TIA, Ross