1957 brake pedal drifting | Ford Thunderbird club group 1955-2005 T-Bird models

1957 brake pedal drifting

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aub

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Thunderbird Year
1957
I purchased a 57 bird with a few problems, Brake pedal was not holding solid and drifting to floor installed new master cylinder and bled system pedal now holds solid but when released and reapplied pedal goes almost to floor
anyone had same issue and found cure

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You still have air hiding in the system.I made a plate with an air fitting on so you can C clamp it tighton the master, so you could pressurize the system . You[ll only need 1 or 2 pounds of air to make this work. Now you can go to each wheel cyslinder , attach a clear hose which goes into a small clear container. Now when you bleed you'll see the air bubbles therefore knowing when that wheel is clear of air. don't forget to keep refilling the master with the fluid from you clear bottle. I'm guessing in using that method you'll find a lot of air from one wheel but don't stop thinking you fixed it. do all four and you'll find the brakes never working better. good Luck!
 
I forgot two things. 1. everything you need you can buy as a kit. 2. The kit will have also fitiings so you can bleed the master. It will allow you to disconnect your brake lines and cannect your bleed lines so by pumping the pedal you'll just run fluid rite back into the reservoir and see that there's no air.Start there before going to the wheels.Good Luck!
 
aub said:
How do you check booster?
Click to expand...
I'm not convinced your problem is air in the system. If you had a firm pedal that suggests there was no air. If on a later application the pedal goes to the floor that suggests a leaking master cylinder (some new ones are bad out of the box) or leaking booster cylinder. Since you just put a new master on it it's more likely the booster is the culprit. The booster is two parts, the "boosting" part which is the big diameter vacuum chamber, and a second part that amounts to a second master cylinder... which, like the regular master on the firewall, can also wear out and leak internally and "go to the floor". If the boosters master leaks the real master will keep pushing fluid into the booster master to move it's piston down. There is another place that can leak in the booster assembly and that is the piston in the control valve part, it could be letting pressured brake fluid leak out which would also let the brake pedal go down but I would expect that to be more of a slow leak rather than a pedal to the floor leak. I don't know if you would see that leak or if the vacuum system would suck it up and hide it. I think it might get sucked into the vacuum chamber. Often when they are taken apart there is brake fluid in them. There are also seals which could potentially leak on the back side of the booster master which is where the rod goes that provides the extra boost from the vacuum chamber to the booster master piston. These boosters have a lot of seals and areas where things can go wrong. For the way these are set up it is possible to cut the whole booster out of the circuit and just hook the firewall master directly to the distribution block on the frame and revert to manual brakes. That is what I did on mine after going thru three boosters, none of which worked right despite being either new or rebuilt. The manual brakes work fine, just takes a bit more effort.
 
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