Brake Problem

[C3forME]

Went to go take the car out today for spin and noticed when I started it up that the brake light on the dash was lit. The first thing I did was check the emergency brake to see if it was on. When I step on the brake pedal it goes all the way to the floor, however with the car off the pedal feels almost normal. I checked the brake fluid in the master cylinder and it was full, and I checked under the car for leaks as well. The vaccum line from the power brake booster looks okay, does anyone have any idea of what the problem could be?

 

[BORDERBUM]

C3forME,

I am not a mechanic or pretend to be one on tv, but I have had this problem on my 77. It was caused from air in the brake lines. I bled the brake lines and while I was at it, I replaced the master cylinder. I am almost sure that it (MASTER CYLINDER) was not bad, but it wasnt too much money and it was old. But as I was bleeding my brakes I could feel the firmness come back to the pedal. Good Luck and hopefully if I am not right ( or just got lucky fixing my own) someone will chime in and point you in the best direction.

GIT R DONE___________________________BORDERBUM

 

[MaineShark]

I agree. Bleed the lines. Only costs a few bucks, and will probably solve the problem.

Joe

 

[69vettester]

Bleeding will probably solve the problem for now. Mine started doing the same, I found out its inherent with the old delco moraine calipers. As rotor runout increases with wear or warpage, air will start getting through the caliper seals and collapse the peddle.
Tom

 

[Vette/Berlina-coupe]

-need to check for aged Caliper-seals...

-all of the above regarding this very serious condition (most d-an-n-g-e-r-o-u-s!), ---this being such a chronic-problem I suspect some "forgiving" degree of runnout at the culprit rear-calipers may be sustainable provided one has relatively "fresh" (ie: very resilient and ware-free) seals in the caliper-buttons [note- this is only speculation on my part, --from my limited experience with these brakes]! -Otherwise, other than "zeroing" any possible runout of the Rotors (only possible via machining on the car), --the commercially available "O"-ring seal type caliper-buttons (instead of original flange-seals) is apparently another viable remedy which serves to better resist air-pumping via the flange-seal's almost flutter-valve like action when oscillated by the impinging Rotor (if out of true)...
~Bob vH

:dance

 

[buddaman]

I just ran into this problem, sounds identical, no fluid leaks though my pedal was only 50% of the time on the floor.

I bled the brakes all around first, essentially changing the brake fluid I bled them so much, didn't help. I changed the front calipers and bled a bunch more and though the old calipers looked worn, it didn't help. Finally, I changed the master cylider and that fixed it.

The key for the master is bench bleed per the instructions, otherwise it's not that bad a job. You could also bring it to the man, brakes are so critical and notoriously iffy in these cars as I'm learning, messing with them unless you really know what you're doing is chancing it.

Master is only a $40 part, labor to install and bleed shouldn't be bad, $150 or so at a mechanic you trust.