: 84 Deville "Brake" light on

05-14-09, 12:16 PM
On my 84 Deville the brake line that goes from the front to rear was rusted out in a spot. I had no power in the rear. I replaced all pads, and shoes, replaced the line, and put new fluid in and bled all four brakes in order. I got the "BRAKE" light off and was happy and had nice stopping power.After all that the brake light would come on and go off only when the car was started. That was ok. I was ready to get my car inspected, because it will fail if it has the light on. Now the light just stays on and when I go to stop, it stops fine, but I have a faint hissing noise coming from the rear drivers side drum area.This happens only when I am moving and the pedal is pushed. Does this have something to do with the adjusters in the drum? There are no more leaks from my lines.

05-14-09, 05:44 PM
Three reasons I can think of to turn on the light..
leaking brake fluid
air in system
emergency brake is on...

05-14-09, 06:10 PM
Or low fluid in master or the belt driven vacuum pump is weak. There is a vacuum sensor in the booster to alert you to weak vacuum. Could be the reason for the hiss??

05-14-09, 07:47 PM
Ok so I pulled off the passenger side drum and found the wheel cylindar was leaking. I replaced that and will bleed the brakes tomm. Hopefully that was the problem.

05-14-09, 09:47 PM
And if fluid got on the shoes AT ALL, replace the shoes again

DopeStar 156
05-15-09, 12:14 AM
I was gonna say check the wheel cylinder, sounds like you nailed it.....

05-15-09, 09:48 AM
Yes, the only things that will turn that light on will be either a leak (as you have found), or the parking brake on.

Carnut is right, new shoes if they got wet.

05-16-09, 09:58 PM
I relaced the cylindar, tried bleeding the brakes, but when assistant pumped the pedal I noticed bubbles in the master cylindar is this normal or does that rubber seal need to be replaced at some point? I did get some much more firm braking action, but light still continues to shine.

05-16-09, 10:07 PM
Assuming ALL air is gone, then sometimes the proporsioning (sic) valve needs to be re centered. Its located below the master. With firm pressure on the pedal, crack the line going to the front brakes to center the valve within the metering block and quickly re tighten.

05-16-09, 10:44 PM
Yes, carnut is right (as usual). The valve is notoriously stubborn to re-center sometimes after a leak has happened. I faced the same situation when I popped the main line to the rears on my 71 Pontiac when I first got it. After replacing the line, and a thorough bleed, the light wouldn't go off. A couple of hard stops caused it to reset.