Ford 2002 F650 Owner's Manual page 213

Maintenance and Specifications
• Caterpillar 3126 B engine
Replace the air filter element using the following procedure:
1. Set the parking brake and shift into N (Neutral) (automatic
transmission) or 1 (First) (manual transmission) and turn the engine off.
2. Open the hood. Protect yourself from engine heat.
3. Push in and turn the latches that retain the air filter housing cover
counterclockwise 90 degrees, then carefully remove the cover.
4. Carefully remove the air filter element. Use caution to keep dirt
and debris from falling into the engine. A twisting rocking motion
may be needed to break the seal between the filter element and the filter
housing.
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