In 1997, Ford Motor Co. decided that the Explorer was lonely and needed a friend to go romping in the mud with, so it released its nearly identical twin the Mercury Mountaineer. The 2003 Mountaineer came with two drive lines, two-wheel drive and all-wheel drive. Both of these drive lines used the same basic suspension setup and replacing the upper ball joint on them meant replacing the entire upper control arm as well. Replacing the upper control arm and ball joint on the 2003 Mountaineer is a straightforward task that most do-it-yourself mechanics can perform.
Loosen the front lug nuts and raise the front of the Mountaineer with a floor jack. Slide jack stands under the sport utility vehicle's frame rails and lower it onto the stands.
Remove the lug nuts and pull the front wheels off the Mercury. Remove the axle nut.
Unfasten the upper ball joint nut with a ratchet and socket. Position a Pitman arm puller over the ball joint, so its screw part contacts the ball joint stud and its claws wrap around the top of the front steering knuckle. Tighten the Pitman arm pull with a ratchet and socket until the ball joint pops from the steering knuckle.
Remove the two upper control arm-to-frame nuts with a ratchet and socket, then pull the shims from the upper control arm studs. Pull the upper control arm up and off the vehicle.
Guide the new control arm with ball joint onto the SUV, sliding the studs on the inner part of the arm into its holes in the frame. Slide the shims onto the studs and hand-tighten the nuts onto the studs.
Pivot the upper control arm downward and guide the upper ball joint stud into the hole in the top of the steering knuckle. Hand-thread the nut onto the upper ball joint stud.
Torque the upper ball joint nut to 38 foot-pounds and the control arm nuts to 111 foot-pounds, using a torque wrench and socket.
Repeat steps 3 through 7 to replace the upper control arm and ball joint on the other side of the Mountaineer.
Reinstall the wheels on the front hub and hand-tighten the lug nuts. Raise the vehicle off the jack stands with a floor jack and lower it to the ground. Tighten the lug nuts, in a crisscross pattern, to 100 foot-pounds.
Drive the Mountaineer to a local automotive repair facility to have an alignment performed.
