Lately I've been having some issues with my car that I think all have to do with my Brake Failure light. The warning light is illuminated in the dash, but I'm not too sure why. The switch (whatever that is) is supposedly working, and the Master Cylinder is in good condition, as far as I know.

My Brake Failure light came on for the first time while driving last week. Here's my post on the matter.

We took the car into the shop, after the mechanics looked over it the first time, and the rear brake pads were replaced. The Master Cylinder did not fall apart or "break" during the repair, so it was not replaced. As far as we can tell, it's still working properly.

Yesterday the Brake Failure light came on for a second time. I noticed it in the afternoon, and so I planned to take the car by the repair shop after work. The mechanic had said to let him see it, should the light come on again. However, on the ride home (perhaps during a hard left U-turn in a parking lot) the light went off, and so I did not go to the shop (there was nothing to see).

However, this morning, the light greeted me when I started the car. It seemed a little brighter than it had been before (check out the above thread to see how it was dim the first two times). I pumped the brake pedal, in hopes of causing it to go off, and after ten or so depressions the RPMs of the motor dropped and the car came somewhat close to stalling. They immediately rebounded, and I stopped to see what would happen. The idle was pretty smooth.

So, I tried it again. Again, after depressing the brake pedal a number of times, the RPMs dropped by a visible (tach) and audible amount.

I drove to work. The brakes seem to work the same, and the stopping power is consistent. There's none of that pedal-to-the-floor stuff from a leaking Master Cylinder.

When I stopped and put the car in Park, I tried again. This time, I could not get the RPMs to fall when the brake pedal was depressed.

I haven't noticed any leaks, but I haven't looked too hard either. At work, I parked on gravel and grass, so it was a little tough to see if there was a puddle of anything. When I get home, I'll check to see if there are spots from this morning, and I'll keep an eye out for any new ones.

If the Brake Failure light is still on after work, I'm going to take the car to the shop. Hopefully they can figure out the problem, though I wish it would resolve itself on its own.

Does anyone have any idea what my problem could be?
Does anyone know why my RPMs drop when the brake pedal is pushed a bunch?
--
'89 244 GL -- 105,XXX miles (see profile for info on car)