1983 Mercury Grandmarquis Brake Indicator Light

Is it normal for the brake indicator light (on the instrument panel.... the same one that comes on when the parking brake is on) to come on when you stomp on the brakes pretty hard?
This happens, even when not moving, such as in park or neutral, of you mash it to the floor, it'll come on, and then go off when I let up. However, when moving (say 35 Mph), and then stomping on them really hard (but nto quite locking up the wheels), it'll come on, but then it will sometimes stay on after letting off the pedal.
This light was on about a week ago, I bled the rear brakes, since I let the resivour for therears get too low and got air in the line, and the light went off. I just happened to notice that the light came on during heavy braking.
Normal or not?
Thanks
Nic
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Check the reservoir again, and you still may have air in the lines and/or proportioning valve.
Robotnik wrote:

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I checked the reservoirs right after I noticed this issue, they're both still topped off.

the
mash
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the
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snipped-for-privacy@asdf.com says...

When the plunger in the proportioning valve is pushed off center it will trigger the brake light to indicate there is something wrong with the brake system.
I would bleed the entire brake system and see if the problem goes away. If not I would check for rusted through brake lines or leaks at the brake calipers or wheel cylinders. If those check out OK then you might just need a new proportioning valve.
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Robotnik wrote:

sounds like you are low on brake fluid,,,,, check the master cylinder out and add some fluid....
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Nope, that was the first thing I checked when this issue arrised, both are nearly overflowing.

the
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An overfilled reservoir can also cause the light to come on. If the reservoir has a fill line or arrow pointing to a fill level, fill the reservoir only to that point, after system has been charged (start engine, run for about a minute, and turn engine off).
Robotnik wrote:

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Yes and no. The warning light is there to tell you have a problem. Most likely the brake linings are worn out.

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I think the only things that influence that light are the Parking brake, and the proportioning valve.
Within the two years, I think just about everything in the braking system as been re-done, except the brake lines themselves. New master cylinder, power brake booster, new rotors on the front, new calipers on the front, new pads on the front, new cylinders on the rear, turned the drums, new shoes on the rear.
Is it unheard of for a proportioning valve to croak?

the
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panel....
you
you
However,
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light
heavy
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