Could be one of two things: 1. Check your tail light fuse and your brake switch fuse; 2. If your fuses are good it's probably your brake lamp switch located behind your brake pedal.
Under the hood, driver's side attached to the firewall
bad master cylinder
No
Under the hood. Drivers' side attached to the brake booster on the firewall
Save yourself some grief and take it to a repair shop
cruise control switch
CHECK the brAKE LIGHT SWICTH ABOVE THE PEDAL ANOUT 10 inches ,by chech see rear brake lights work. CHECK the brAKE LIGHT SWICTH ABOVE THE PEDAL ANOUT 10 inches ,by chech see rear brake lights work.
go to markviii.org. they have a answer for almost anything with the lincoln mark viii
If you mean the brake light, you just have to change the bulb or bulbs.
in the panel located on side of dashboard open drivers door to see it
If you mean that you can't shift the shifter while pressing on the brake, I would say that it is down by the brake pedal.
Someone with a service manual should chime in, it will be in there.