I have a 2006 F150 that the brake light keeps coming on and off. I'd say its on about 75% of the time now. All the pads have been replaced, changed out the overhead brake light bulb, changed the master cylinder sensor, and I've disconnected and reconnected all the wire connections I could find. The best I've been able to do is get it to turn off for about 24 hours and it pops back on. I was told yesterday that it could be a bubble in the line or old dark brake fluid giving the sensor a false reading. I figure for about 10 bucks doing a flush would be worth a try. Everything I can find shows lifting the entire vehicle and removing all 4 wheels. Would there be an issue lifting one side at a time or even leaving it on the ground as long as I can get to the bleeder valve?

Any other ideas of what the issue might be that is causing the warning light to keep coming on?



I am pretty new to doing my own mechanic work so please excuse any dumb questions. I am pretty mechanically inclined and I would have been doing this a lot earlier if I knew how easy most of it is.

 

Could be the parking brake switch, that also can turn on the light.

 

I agree with glc, could be the switch on the parking brake.
As for having to lift the vehicle, no you can bleed them all w/o lifting it if you can reach them. Be fore warned that they're easy to break if you get too rough with them. I've found if there's room for a ratchet and a SIX POINT socket you're less likely to snap one off using that to get them loosened, then using a wrench for bleeding.
Gene

Side note, use brake line wrenches or 6-point sockets to prevent stripping the fittings. They are easy to strip because they're generally soft metal

 

there are no sensors that would detect "old dark fluid".

and it is doubtful even that your ESP system could detect a bad bleed. (newer systems can)

Have you had someone check the codes?

Most likely cause is either a bad FLI (Fluid Level Indicator) switch on the reservoir, or the parking brake pedal being slightly depressed.