Brake problems

Which brake light are you referring to? The light on your dash or the actual brake lights of the car? If the latter, it is most likely the switch on the peddle, the peddle may be slightly depressed at rest (just enough to activate the switch). You can verify by pulling the brake peddle out. If this is the case, you need to complete the bleeding process as that may be why the peddle is 'sagging' and activating the brake light switch.
 
One other question for you; does the master cylinder have vacuum assist? If so, have you checked your vacuum lines?
 
The brake light in the dash. No the master cylinder doesn't have a vacuum assist. The brake booster is on a vacuum line. And the brake booster works. The problem is if you hit the brake pedal once (running or not) the brake is soft pump it a couple more times it starts to get harder likes its working. Let off the brake wait 10sec and same thing
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There should be a brake proportioning valve with an electrical sender, you have tripped it by the process of bleeding or because of the problem you are trying to resolve. Have you found out the exact master cylinder part number from autozone? have you compared the diameter of the master cylinder piston that originally came with the car with the one from autozone?
 
The proportioning Valve on it does have one and it is plugged we plugged it in. The master cylinder part # is nm1745
 
I actually saw a what looked like a pin or button on the end of the prop valve. Ill have to try this when I get home edit. I was thinking and we get good pressure when bleeding the brakes. The fluids squirts out. But I will try anyway
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Ok well we jacked up the rear of the car and bench bleed the master cylinder still on the car but it just squirted fluid. We then bleed all the Brakes and in the order you said with a hammer. I pushed the reset on the prop valve and it popped back out after we pumped the brakes. Still the same thing. We clamped a vise grip to the rear lines and the pedal got hard. Let the vise grip off and pedal went down. Ok we bleed them more. Same thing. We clamped the front brake and same thing. Any one of the rubber lines that you put a vise grip on and pump up the brakes and take the vise grip off the pedal goes down. We got to thinking and have a 1972 brake booster on car it flat and short. Could this be the problem? Do we need the 79-81 booster?
 
the only issue you could have with the booster is that the pushrod coming out of the booster isnt touching the brake master piston. The rod might be adjustable.
 
What if its not adjustable and we also don't the the e brake hooked up. Could this affect it
 
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Start off with measuring it, if you have a copy of the 1971 factory service manual it is covered on page 5A-10. If you dont have the proper clearance you will need an adjustable rod. The fact that you are mixing different year parts may contribute to having the wrong clearance. Was this conversion a kit and if so do you know who made it and if you do have you tried contacting the manufacturer?
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We measured it all the way out is about 13/4 inch it is not adjustable. We bought it with the conversion kit on it but don't know what brand it is. Should we buy the longer 1979-1981 booster for disc brakes
 
I take it you dont have the shop manual. You measure the distance with the engine off and the rod fully retracted. The idea is there should be minimial distance between the rod and the piston in the master. Too much clearance and the pedal goes too far down, too little clearance the brakes drag. I have no way of telling you if the 79-81 booster will just bolt on without causing you more issues.
 
I just looked up brake boosters in the Firebird catalog from www.amesperf.com and the 79-80 4 wheel disc used a different booster than the 2 wheel disc.
 
That's what I've been trying to say all along is there different. I think cause they push more fluid than the drum cause calipers hold more fluid than wheel cylinders.
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One would expect whoever got the original idea to make the conversion would have gotten a complete kit rather than piecing it together afterwards. Have you downloaded the ames catalog and looked at the booster?
 
We have the Ames magizene at out house. My grandpa has a 1979 10th an and the booster is longer but not as big diameter I think my dad ordered a 79 disc brake booster last night. Hopefully this fives the problem. I asked my dad if we could call the guy who sold us this car and ask what conversion kit he used but I don't think he's going to. The guy runs he's own business and is really busy
 
Your dad ordered the 79 for 4 wheel disc, correct, it is different from the 2 wheel?
 
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