Intermittant Brake Light on dash

[jdodman]

After installing a line lock and new Master Cylinder on my 1987 GN, I have a brake light that comes on/off without reason. I can always shut it off by tapping the brake pedal, but not sure what is bringing it on. Bled the lines several thousand timez with no improvement. Is there a sensor or something electrical that is going bad or throwing a false positive on the brakes ?? Fluid is right where it needs to be, no clue what else to try, short of pulling out the light bulb ...That is next..

 

[John Larkin]

Bled the lines several thousand timez with no improvement.

LOL! I know how you feel. One thing I had to do (and am still not satisfied) is start from the beginning. Gravity bleed the master cylinder; what I mean is loosen the fittings until fluid drips a good bit out onto a rag underneath, maybe give it a few slow pumps. Tighten that, then move down to the line lock. Do the same there; no pumping needed but crack open both ends of the line lock, inlet first, outlet second. Then you should be pretty free of air in that portion of the system.

After all this, rebleed the sequence around the car. Try to stick with the gravity method; pumping brakes requires restricting the prop valve metering rod movement. I think gravity bleeding works fine.

The light is due to an imbalance in pressure front and rear. One thing you could try before going through this hell all over again is open the master cylinder cap slightly and slowly/repeatedly pump the brakes. I did it once about 20 times and the light finally went out with car running in park. Just don't create Old Faithful squirting out the top; pump slow and steady. Hope this helps. Probably some contrarian points of view out there as well.

 

[TurboDave]

You should only see the brake light during and after you apply the line lock. It'll go out as soon as you tap the brake pedal after you've used the line lock (like when approaching the line). That's faily normal because when applying the line lock, you've unbalanced the system, hence the light.

Is yours coming on at other times when not using the line lock?

 

[jdodman]

It absolutly comes on/off when I use the line lock and I already decided that was part of the issue. But when I am braking hard under normal conditions it comes on (like exiting a highway exit ramp), then I have to tap it a couple of times and it subsides. I can go 4 weeks not seeing a thing, then it is on 4 times a day.
Driving me crazy.. I will try to bleed one more time, then the bulb is on the side of the road.

 

[Rollin]

gone to tech