DOT 3
According to the 1996 Mercury Grand Marquis Owner Guide : ( DOT 3 brake fluid , meeting Ford specification ESA-M6C25-A )
Why ? Just replace it.
check your brake lights if they not worhing replace fuse or brake light switch
According to the 2001 Mercury Grand Marquis owners manual the fuse panel is below and to the left of the steering wheel , by the brake pedal , and has a cover on it
its either a dead short or not properly grounded check that out
to the left of the brake pedal, mounted to the firewall.
driver's side , inside the car, near the parking brake.
The red " BRAKE " light in your dash means that either your parking brake is on or the BRAKE FLUID LEVEL in your brake master cylinder in the engine compartment is LOW
change the brake lights check the fuse check the brake light swtch
The problems are connected The power that runs the brake lights releases the shifter from park. So if you fix why the fuse blows the shifter will work. We service Crown Vics that vintage at work and ran across that problem a few times. Replacing the brake light switch did then the trick.
Remove the wing nuts from inside the trunk, the assembly will pop out.