Brake light coming on
Thread Starter
Racer
Joined: Aug 2007
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From: Quincy MA
Brake light coming on
Had shop do tune up at beginning of '09 season and take care of the mysterious brake light that keeps coming on (red)...so the reputable shop blead the brakes, it's six months later adn about 2000 miles and the brake light is coming on again, what else could this be, mostly comes on under hard stopping conditions...
'74, auto, 350, 63K miles...
Thanks in advance,
Kevin
'74, auto, 350, 63K miles...
Thanks in advance,
Kevin
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From: mount holly NC
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You may have a 'run-out' problem with the rear rotors, if the master cylinder is full but the light comes on when you apply the brakes then bleed the brakes and see if the problem reoccurs. If the problem comes back then check the run-out on the rear rotors.
Thread Starter
Racer
Joined: Aug 2007
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From: Quincy MA
Forgive me in advance, but what 
is "run-out" I am not familar with that term.....I have been getting a squeek for years when I am not applying the brakes, sounds like coming from the rear, so I think you might have hit the nail on the head... 
Thanks!
KO
is "run-out" I am not familar with that term.....I have been getting a squeek for years when I am not applying the brakes, sounds like coming from the rear, so I think you might have hit the nail on the head... Thanks!
KO
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From: Muskegon MI
Runout is the distance the rotor "wobbles" as it rotates. To measure runout you mount a dial caliper and set the pickup on the rotor, then spin the rotor. If the rotor wobbles more than .006 inches you need to have it machined on the car to eliminate the runout. Excessive runout can lead to reverse oscillation (air pulled into the system through the piston seals), poor pedal pressure, and the brake light coming on.
Thread Starter
Racer
Joined: Aug 2007
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From: Quincy MA
That sounds like what it might be...will need my technician to check it out soon as the wifeeeeee gets a lil' nervous when we take an off-ramp at 60-65 and the brake light comes on as I tap the brakes before I hit the apex :-)
KO
KO
Runout is the distance the rotor "wobbles" as it rotates. To measure runout you mount a dial caliper and set the pickup on the rotor, then spin the rotor. If the rotor wobbles more than .006 inches you need to have it machined on the car to eliminate the runout. Excessive runout can lead to reverse oscillation (air pulled into the system through the piston seals), poor pedal pressure, and the brake light coming on.
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From: Dayton, Ohio
If your tech doesn't find enough runout to cause the problem have him check the dynamic balance of the tires. I've seen this coupled with sleeve bores on the high side give this problem.
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Racer
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From: Quincy MA
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Either rotor runout or loose bearings can cause you to lose your brakes and wifeeeeeeeeeeeeeeeeeeeeeeeeeeee will be really upset then.
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From: mount holly NC
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