2001 Grand AM 4 cyl. Brake Light Stays on

[Plzhelp]

Hello:
I've got a 2001 Grand AM 4 cyl. About a week ago the brake light all of a sudden came on while I was driving it. The brake pedal felt a little squishy but nonethless I was able to drive it home. I've since bench bled the master cylinder, installed it; bled the two brake line connected to the cylinder; bled the two brake lines going to the ABS unit, and bled all four calipers in the order specified in the Haynes manual. This car has disc brakes in the front and drum brakes in the back. However, the light is still on and the brake pedal still goes to the floor. My dad said it's probably my master cylinder but everyone else I've talked to says that I have air in the system. I did replace the front disc brake pads about a month and a half ago but that didn't require me to do any bleeding as all I had to do was push the pistons back with a C clamp and then install the pads. Can someone help me please? Also is it possible this may be caused by the ABS unit? Believe the one that's on my car is the Delphi DBC-7.

Thanks.

[Hungrycat7]

I had a similar problem on my wife's Taurus. The pedal would sometimes just go to the floor and the brakes were very unresponsive. Replaced the rotors and the pads and it was still doing it. Did notice one of the pads was far more worn than the others. It turned out the pins were not functioning correctly and it was binding one of the pads. The brake would get insanely hot and actually start boiling the brake fluid. The boiling released air into the system and caused a very squishy pedal. Pulled the pins, cleaned them off, and re greased. Everything has been great ever since

[J-Ri]

If you bled the brakes properly, you don't have air in the system. Hungrycat is right about the possibility of the fluid boiling, but that's not very common. When the fluid boils, it's actually water in the fluid that is boiling, and I wouldn't expect a 7 year old car to have accumulated enough moisture for that to happen.

Since you said you used a C clamp to press in the caliper pistons, I would guess that you are correct about the master cylinder being bad. You should crack the bleeders open and press the piston in very slowly so that most of the fluid comes out through the bleeder. Forcing too much fluid back into the master cylinder can damage the seals. I live in Iowa, and with the rust we get here, I know that's not a realistic option for most cars. When you think the bleeder will break off, leave it shut, but press the piston in VERY slowly. I will usually take 2 minutes per side and put almost no pressure on it. Opening the bleeders will also keep fresh fluid in the system, which means better braking performance, and quite possibly longer brake line life (supposedly they rust from the inside out from the water in the fluid ). Brake fluid is hydroscopic, which means it absorbs water, which is why it should be changed periodically.

[Plzhelp]

Well it turns out the sensor that sits on top of the master cylinder which I think gauges fluid level or brake pressure, I can't remember which one, was bad. I replaced the sensor and the brake light doesn't stay on while I'm driving and it brakes better than ever. Thanks to everyone for all their help. In a way it's all good since my brake fluid needed to be changed pretty badly as it was really dirty. Anyways, thanks again.