71 LT1 brake light help

[Phil M.]

I've just completed a full brake job on my 71 LT1, new brake lines, calipers, rotors, proportioning valve. Now the dash brake light does not turn off. I have no leaks and the car brakes with no problems, no pulling to either side and the brake peddle is very high (as you would expect with a new brake job).
Does anyone have any tips to troubleshooting the brake sensor on the proportioning valve? How could I tell if I have a true brake problem, bad sensor or some other problem. I also changed the parking brake spring and rear cable. Is it possible that the parking brake switch now needs readjusted?

thanks for the help, Phil

[Kevin G.]

Re: 71 LT1 brake light help

Silly but, do you have the emergency brake handle completely down or off?

Kevin

[Phil M.]

Re: 71 LT1 brake light help

Yes, I even moved it up and down multiple times to see if I could get the light to blink indicating there maybe a problem with the parking brake lever sensor. Unfortunately the light didn't blink, just stayed on. But thanks for asking, Phil

[Jeremy D.]

Re: 71 LT1 brake light help

I'd take a closer look at your parking brake switch inside the console, and the wire going to your proportioning valve. In my experience, if everything else is all good, the "brake" light should only come on if there's a leak somewhere ( which with low pressure, the wire to your proportioning valve should turn on the bulb) or your parking brake is on. It sounds like an electrical issue to me more than hydraulic...I guess the best advice I can give is, check your grounds!!!

[Terry M.]

Re: 71 LT1 brake light help

Your 1971 Corvette does NOT have a proportioning valve. It does have a pressure differential valve, and that is what is turning on the brake light on the dash. The pressure differential valve has a small ball in a channel that connects the two ends (front and rear) of the brake system. When the pressure is high in one of the ends and low in the other -- as when you were bleeding the brakes -- the ball is forced toward the side with the lower pressure. The only way to move the ball to the center -- and shut off the light -- is to lower the pressure on the other end. The problem is that unless you watched the light while you were bleeding the brakes -- a very difficult task to accomplish -- you have no way to know whether the ball is toward the front or the rear -- so it is a roll of the dice to try to correct. And of course one can over-correct and move the ball to the other end and still have the light on.

Bleed one end of the car -- either side doesn't matter -- to see if you can move the ball to the center of the channel. If that doesn't work try the other end of the car. Have someone watch the light (ignition will have to be on) while you are doing this. Good luck.

[Phil M.]

Re: 71 LT1 brake light help

Wow, great information, I'll give it a try, thanks Phil