[Smokin_Joe]

When I step on the brakes (66 GT drum/disc), you can feel an initial grab but not enough to stop the car. I have to press further down before the more-serious stopping power comes on. Almost like there is air in the system. And then, it feels like it may not stop. It makes me wonder if I stood on the brake pedal, I'm not sure the wheels would lock. I've rebuilt the master cylinder and the rear brakes. I haven't touched the front calipers but they have what looks like fairly new pads. No leaks anywhere. Brakes hoses are old (one crimp style) but I don't see any swelling or balloning. I've bled all four wheels. It's a bit unnerving and I'm stumped. Any comments/suggestions ??

Vintage Burgundy 1966 Mustang GT Fastback (Midlife's younger brother)
MCA member #46447

 

[Guest]

Could be a bad proportioning valve?

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[66emberglow]

Did this symptom just show up, or was it like that since you did the brake work? I think I would be inlined to take it to a brake shop and let them bleed the brakes with their machine. That way, you can be sure that isn't the problem.

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[Guest]

You've bled all four wheels, but have you bled the master cylinder?

 

[Guest]

I just concluded an ongoing situation similar to yours. I replaced one by one the components as you have described. Still had problems such as fading pedal at stoplights and occasionally having to really stand on the pedal to stop. The only thing left was the proportioning valve and after replacing it this last weekend my problems seem to be over.
Do make sure first though, as previously posted, that the lines are thoroughly bled; you may get lucky.

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[Guest]

Did you bench bleed the master cylinder?

Jon Sherar/(67 Fastback)

 

[Guest]

Yeah, I didn't mention that but yes I did. Outside of bad lines and/or calipers, that's the only thing left.

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[Smokin_Joe]

Yes, bled it before installation.

Vintage Burgundy 1966 Mustang GT Fastback (Midlife's younger brother)
MCA member #46447