All, replaced a leaking master cylinder on my 57 Ford. Worked great when driving around the block, went for a cruise and now the pedal is hard, and the brake lights stay on. I released some pressure near the switch and heard the system “relax”. Drove it around the block and it again the pedal was hard and lights went on.

stumped on this one. Any thoughts?.

1957ford

Did You Bench Bleed the Master and did it return to released Position? I am thinking maybe defective Cylinder. Did You completely Bleed the System to get all the Air out?

  

You need to adjust the pushrod so that you have some freeplay in the brake pedal.  It is not allowing the master cylinder to retract completely.  If you do have freeplay, then check the small fluid return hole visible with the master cylinder cap off and the fluid reservoir empty.  The hole must be open when the piston is fully retracted.

John - "The Hoosier Hurricane"

Thanks all for the feedback. I got it to work by rebleeding the master cylinder. Much appreciated.

1957ford