Tools You'll Need:
* Jack and jack stands (essential for safety!)
* Lug wrench
* Wheel chocks
* Socket wrench set (likely 14mm and 17mm for caliper bolts, and possibly others)
* Torque wrench
* C-clamp or caliper compression tool
* Wire or zip tie (to keep the caliper out of the way)
* Penetrating lubricant (like PB Blaster)
* Rotor removal tool (if needed – sometimes a hammer and punch work, but a tool is safer)
* Gloves and safety glasses
Procedure:
1. Safety First: Park on a level surface, engage the parking brake, and use wheel chocks on the wheels *opposite* the one you're working on. Jack up the vehicle securely and support it with jack stands *before* you remove the wheel.
2. Remove the Wheel: Remove the lug nuts and carefully take off the wheel.
3. Remove the Caliper:
* Identify the Caliper Bolts: Locate the caliper bolts (usually two) holding the caliper to the knuckle. They are typically 14mm or 17mm.
* Apply Penetrating Lubricant: Spray penetrating lubricant on the bolts to help loosen them. Let it sit for a few minutes.
* Loosen and Remove Bolts: Carefully loosen and remove the caliper bolts.
* Support the Caliper: The caliper is heavy and contains brake fluid. Use a wire or zip tie to secure it to the suspension or spring, keeping it from dangling and stressing the brake line. Do not let the brake line hang freely. A C-clamp or caliper compression tool is even better for this as it compresses the piston slightly, allowing for better support.
4. Remove the Rotor: Sometimes the rotor will just slide off after the caliper is removed. If not:
* Inspect for Mounting Bolts: There might be one or two small bolts securing the rotor to the wheel hub. If present, remove them.
* Use a Rotor Removal Tool: A rotor removal tool is the best way to remove the rotor, as hammering can damage the hub. If you don't have a tool, you might carefully use a hammer and a punch (placed against the rotor's mounting surface, not its braking surface) to gently tap it loose. Be cautious not to damage the hub.
5. Clean the Hub: Thoroughly clean the wheel hub mating surface to ensure a good fit for the new rotor.
6. Install the New Rotor (Reverse Order): Install the new rotor and ensure a snug fit.
7. Reinstall the Caliper: Reinstall the caliper, making sure the caliper slides easily and doesn't bind. Tighten the caliper bolts to the manufacturer's specified torque.
8. Reinstall the Wheel: Replace the wheel and tighten the lug nuts in a star pattern to the manufacturer's specified torque.
9. Lower the Vehicle: Carefully lower the vehicle from the jack stands.
10. Pump the Brakes: Pump the brake pedal several times to ensure the brakes are working properly. You may need to bleed the brakes if air got into the lines.
Important Considerations for AWD:
* Wheel Bearing: Inspect the wheel bearing while the rotor is off. Excessive play could indicate a failing bearing.
* ABS Sensor: The ABS sensor might be located near the rotor. Be careful not to damage it. If you do, you'll need to have the ABS system scanned and potentially repaired.
* Brake Pad Wear: Check the brake pad thickness while the caliper is off. If they are worn, replace them as well.
This is a general guide; consult a repair manual specific to your 1998 Mercury Mountaineer for detailed instructions and torque specifications. If you are not comfortable performing this repair yourself, take it to a qualified mechanic. Improperly installed brakes can be dangerous.
