1. Preparation:
* Park and Disengage: Park your Expedition on a level surface, engage the parking brake, and turn off the ignition.
* Gather Tools: You'll need a wiper arm puller. While you *might* be able to pry it off with other tools, a wiper arm puller is the safest and least likely to damage the wiper arm or the wiper arm mounting point. If you don't have one, consider buying or borrowing one before proceeding. Trying to improvise could lead to damage.
2. Removing the Wiper Arm:
* Locate the Nut (Sometimes): Some wiper arms have a small nut underneath a decorative cap. If you see this, remove the cap and unscrew the nut before proceeding with the puller. This step isn't always necessary on a 1999 Expedition, however.
* Position the Puller: Place the wiper arm puller's claws around the wiper arm base. Make sure the claws are securely gripping the wiper arm, close to the pivot point.
* Apply Pressure: Slowly and firmly tighten the puller's adjusting nut (usually a screw). This will apply pressure to the wiper arm, separating it from the mounting post. It's a leverage action; you're separating the arm from the splined post, not unscrewing anything.
* Wiggle and Remove: Once the arm starts to loosen, gently wiggle it back and forth. The arm should now separate from the pivot point. If it's stuck, don't force it! Check the puller's placement and apply more pressure gradually.
Important Considerations:
* Rust and Corrosion: If the wiper arm is very old or rusty, it might be very difficult to remove. Penetrating oil (like PB Blaster) applied several hours beforehand can help loosen it up.
* Force: While you need to apply firm pressure, avoid excessive force. You could damage the wiper arm, the mounting point, or even break the windshield. If it's stuck after using penetrating oil and reasonable effort, consider seeking professional help.
* Windshield Damage: Be mindful of the windshield. Use caution when using the wiper arm puller to avoid scratching or chipping it.
After Removal:
* Clean the Mounting Point: Once the wiper arm is off, clean the mounting post to remove any dirt or debris. This will make reinstallation easier.
Reinstallation: Reinstallation is the reverse process. Make sure the arm is properly aligned before tightening the nut (if applicable) or fully seating the arm onto the pivot post.
If you're uncomfortable performing this task, it's best to take your Expedition to a professional mechanic. They have the tools and experience to do it safely and efficiently.
