Okay, WHAT is going on with my brakes??!

[MopaR&D]

For the past year or so I've had to put up with a "soggy" brake pedal. I have manual front disk brakes on my '70 Duster (yes they are the Kelsey-Hayes) with pads and shoes in good shape. After replacing a front rubber brake line and bleeding the brakes (which took almost a whole 1-liter bottle of brake fluid) on the front side I fixed as well as both the rears the pedal had firmed up nicely. However only a day or so later and the pedal was soft again; it will go down about two inches and then suddenly firm up. I also have to make sure I press the pedal with some quickness, as the pedal slowly sinks all the way to the floor if I gently put my foot on it. It seems like air is getting into the system from somewhere, as I kept getting bubbles when I was bleeding the brakes even though I was sure nothing was leaking. Could this be a master cylinder issue? If so where should I get a good one from, as my current one is a remanufactured MC (I think Cardone or whatever) I got two years ago from Checker.

 

[slantsixdan]

Cardone = crap.
Checker = crap.
"Remanufactured" = crap.

This what you're experiencing is typical of a master cylinder with leaky seals: when you hit the brake pedal hard, the seals flare and make a decent seal. When you slowly apply the pedal, the seals don't flare and fluid runs past them.

Put on a new master cylinder, Raybestos #MC36426. Make sure you bench-bleed it thoroughly before you install it. Your trouble will go away.

 

[demon seed]

If the peddle is going slowly to the floor and you're sure ya got the air out of the system then your master cylinder piston is bypassing. IMHO

Terry

 

[caferacerx]

have had the same problem on a number of vehicles over the years a new master cylinder as recommended by slantsixdan has always fixed it