67 Brake issue help!

[Michael W.]

Re: 67 Brake issue help!

The new booster seems to be working although the pedal goes to the floor and the "brake" light lights.

Ah- there's the key. The light will only come on in response to a flow/pressure imbalance between the front and rear brake systems. A booster or pedal issue cannot cause this.

As other have said, bleed the brakes.

[Mark C.]

Re: 67 Brake issue help!

OK sounds like I will be bleeding the lines. Should I flush out the lines and replace the old fluid? I think the car sat for a long time without running much. Should I replace the master cylinder ????
Mark

[Michael W.]

Re: 67 Brake issue help!

I'd flush the lines and see what happens to the pedal. No need for a M/C at this point.

[Mark C.]

Re: 67 Brake issue help!

should I refill with synthetic fluid?

[Brian M.]

Re: 67 Brake issue help!

All DOT 3 & 4 brake fluid is synthetic to the best of my knowledge. I use DOT 4.

[Michael W.]

Re: 67 Brake issue help!

If you mean DOT5, don't allow that to mix with DOT3, 4 or 5.1 type fluid, They are non-compatible.

[Mark C.]

Re: 67 Brake issue help!

UPDATE
I was debating if I should change the master cylinder out anyway and after I took a good look at mine I realized that my old MC was incorrect. I replaced the old one with a correct new and the car now stops! Thanks for ll your help.
Mark

[Paul J.]

Re: 67 Brake issue help!

UPDATE
I was debating if I should change the master cylinder out anyway and after I took a good look at mine I realized that my old MC was incorrect. I replaced the old one with a correct new and the car now stops! Thanks for ll your help.
Mark

Thanks for the update, Mark. As I described before, when you have a pedal that goes all the way to the floor without stopping, either suddenly, or slowly under firm pressure, the seals in the master cylinder are allowing the fluid to pass, hence not building hydraulic pressure in the lines. This is caused by old seals and o-rings or by pitting in the cylinder (or both). What you experienced were the classic symptoms of this failure.

If you had air in your lines, the pedal would be spongy, but it would stop before it got to the floor. You can pump the pedal to firm it up and that's why Ed suggested that you bleed the lines. If you have'nt already done that, you should still do it.

Paul

PS I took Driver's Ed in 1970. We had a coarse painted on the parking lot behind the high school, and we had cones and sticks cemented in coffee cans around it. After only an hour behind the wheel, I pressed the brake pedal on the 66 Ford I was driving and it went straight to the floor allowing me to back over a bunch of sticks and cones and hit the curb, finally stopping. When I pressed it the next time it worked fine. My coach was also my Driver's Ed instructor and he let me have it until his assistant (who was in the car) told him the MC had failed. I've been interested in brakes ever since.

[Mark C.]

Re: 67 Brake issue help!

Paul,
All lines and MC have been bled
Thanks again
Mark