Fluid Venting/Foaming
WARNING: This page does not describe the selected car, but rather 9 other vehicles, including the 2002 Lincoln Navigator, 2002 Ford Expedition, 2001 Lincoln Navigator, 2001 Ford RV Cutaway, and 2001 Ford Pickup. However, it is still accessible from the selected car via links, so may be relevant.
Blocked or damaged vent, overfilled, fluid contamination (coolant or water), overheating, pump inlet filter and seal, and pump to case gasket damage.