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Brake light "on"

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labboy

Freshman Member
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I recently purchased my first MGB a '78.
The brake light is on, I had the brakes checked, almost new but the fluid was a little low.
They topped off the fluid, brake pedal is more firm now, but the brake light is still on.
Is this an indication of a more serious problem?
Thanks for the help.
Gary in Red Wing, MN-Home of the Boots.
 
Could be a couple of things.

First, make sure the hand brake is fully released.

Second, last time the brakes were bled on the car, they may not have done it right. There is a pressure differential switch in the brake circuit. When the pressure is different between the front and rear brakes, the light goes on. If not bled properly, the light will go on. Bled a little from one end of the car and see it the light goes out. If not, try the other end of the car.

Lastly, a little low on the fluid is not necessarily unusual since as the fron disc pads wear down, more fluid fills the the caliper and your fluid level drops.

However, if you do have a leak, even a small one, the light will go on and stay on till repaired.

Mike
 
Hi Gary,
Guess I doubled with Mike.
It's likely that the pressure failure switch needs to be re-centered. There is a shuttle operated switch that is off unless unequal hydraulic pressures move the shuttle off center. Normally when the two separate hydraulic systems operate there is equal pressure on both sides of the shuttle & it stays centered (switch off). If one half of the system leaks or fails, the pressure in the good half pushes the valve off center & the light comes on. It could easily get off center during brake bleeding.

To re-center the valve, loosen one of the MC output fittings slightly & depress the pedal slowly until the light goes off. If this doesn't work, tighten the fitting & loosen the other one. Repeat depressing the pedal. It may take both tries, since we don't know which way the valve is off center. When you get the light out, tighten the fitting & you are done.
D
 
Dave,

What is an MC output fitting? or what does the MC stand for?

-Doug
 
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