[meyousikmann]

I bought a '78 T/A last spring and the brake light has been on since I bought it. I have only driven it about 3 times since I got it because I am not comfortable driving it with the brake light on. So this weekend, I decided to put new brakes in it. Bear with me as I am a complete novice at auto mechanics, but I am learning. Other symptoms of brake problems was a soft brake pedal and the right rear would always seem to lock up if I pressed hard enough on the pedal while the other three did not. I put new pads and shoes on and replaced both rear wheel cylinders while I was at it because one of them was leaking fluid. I bled both the front and rear then put everything back together to test. I did several forward and reverse motions to adjust the rear brakes but the pedal still seems to travel way too far and the brake light will not go out. Where do I go from here? Is it possible the master cylinder is bad? How would I know? I appreciate any help you guys can give me.

[Skip Fix]

I think my 78 had the valve in the proportioning valve that you have to reset.I'll check th emanual tonight. Some prop valve that control front and rear have a kind of a bypass that shuts down and leaves the light on. You have to hold it down while someone get some pressure in the line. Could be why the other three aren't good either.

[meyousikmann]

Thanks for the info. I am curious to see what you find in the manual.

[mothermuxer]

Are you getting a hard pedal after pumping the brakes?

The prop valve portion that controls the front is a metering valve, and that's the little pin that pops out when you depress the brake pedal. You'll have to keep the pin from popping out from the prop valve (it's under the rubber boot... if that's still even there... facing the engine opposite of the rear brake line). If you don't want to deal with the pin, gravity bleed the brakes, as it usually works best anyways.

Pedal height is also attributed to adjusting the parking brake cable under the car. But it sounds like you've got air in the system, or a bad master cylinder.

[TransAm525]

1. Reason for the light being on: There is air in the brake lines. Once the pedal reaches a certain displacement, the light will come on indicating a problem within the system. I had a 1982 Corvette that did the exact same thing. Bleed the brakes and the light will go out. If the pedal is nice and firm after bleeding the brakes and the light is still on, it might be possible the parking brake switch, which activates the brake light as well, might be sticking.

2. The reason for the right rear wheel locking up is due to a bad wheel cylinder. What happens is one piston in the wheel cylinder seizes first, while the other still works. When you push on the brake pedal, that one piston pushes the brake shoe on only one side and binds the system up because the other isn't working, thus causing the wheel to lock up. Replace the wheel cylinders on both rear wheels and your problem should be solved.

[meyousikmann]

Thanks for the responses, guys.

TA525, you hit the nail on the head for both points. As I stated in my original post, I replaced both rear wheel cylinders and the single wheel lockup problem was solved.

With regard to the light still being on and the excessive pedal travel even after new pads, shoes, wheel cylinders, etc...., turns out it was the master cylinder on that one. After replacing it and bleeding the entire system, the light has gone out and the pedal action feels normal.