What is the size of idler arm on a 1999 ford expedition Eddie Bauer with 5.4 L engine?

There isn't a single "size" for an idler arm in the way there might be for a bolt (e.g., 1/2" x 13). The idler arm itself is identified by its part number. To find the correct size/part number for your 1999 Ford Expedition Eddie Bauer with a 5.4L engine, you'll need to:

1. Consult a parts catalog: Use an online parts catalog like AutoZone, Advance Auto Parts, Napa Auto Parts, or RockAuto. Enter your vehicle's year, make, model, and engine size. Search for "idler arm." The catalog will show you the correct part for your specific vehicle.

2. Check your existing idler arm: If you can still access the old idler arm, the part number is likely stamped on it somewhere. This is the most reliable method.

3. Consult a repair manual: A Haynes or Chilton repair manual for your vehicle will list the specifications of the idler arm.

Important: Do not rely on general dimensions or assumptions. Using the wrong idler arm can lead to poor steering performance, premature wear, and even safety issues. Always use the correct part number specified for your vehicle.