How do you tighten the parking brake cable on a 1998 Mercury Mountaineer?

Underneath your vehicle, a steel threaded cable comes from the back of one hub and is joined by a short cable from the other hub--then the original cable runs to a threaded end with an adjuster nut in it--and one smaller nut on the end outside of that--(this is the equalizer bar)--you'll see it real close to your transmission.

You might have to jack-up the back of the vehicle???

Pull the parking brake lever up sharply and then release it. Pull the parking brake lever to the second click and leave it there. You're looking for a slight drag of the brake shoes when you spin the wheels. To increase the drag, get under at the equalizer bar and turn the adjusting nut to take up the slack in the cables. Get out and spin the rear wheels if you think it's to tight. I will say don't be afraid to crank on it for a while as in this case, a little adjustment really does not go a long way. When you think you have the drag right, go back in the car and pull the brake up the the fourth click. At this point the wheels should be locked and you should not be able to turn them even when trying hard. If you can, tighten them up a little more. Once you've done this, release the brake and make sure the wheels spin freely. If they are still binding due to the parking brake, back off the adjustment a little. And that's basically the whole adjustment procedure.