Brake Dash Warning Light Mystery

[crow]

Hello Everbody ,
I have a mystery with my 73 , that's even has my mechanic is shaking his head over , first some history I put a new LF caliper on then bled the brakes, worked fine 2 days . Next morning the petal when to the floor and the brake warning light came on , that night checked it out, brake line was loose at master cyl. Bled the brake again , next morning petal down and( brake warning on) but not as far as before, drove the car to work and the more I drove it the better the braks fill (light off), in fact toe touching good , well it's been a week now and the same thing petal down in the morning and great rest of the day . No fluid lose no clues
thanks sorry for the long post
crow

 

[C3forME]

Did you try the check valve and grommet on the power brake booster? I had a slight tear in the rubber grommet and it hissed ever so slightly but made the pedal drop to the floor and prevented the booster from holding vaccum. It took me a couple of days to find the problem because it was hard to hear with engine running, but I was under the hood the other day and heard a hissing noise and started snooping around moving hoses until I found it. I replaced both the check valve and grommet for $7.00, problem solved.

 

[crow]

Thank Larry I will check it out tonight