Engine Noise: Knock

Check for worn rod/main bearings.
Check for loose piston pins.
Check piston to cylinder bore clearance.
Knock (Detonation) - See SPARK KNOCK under SYMPTOMS.

NOTE: For additional A/C system information, see appropriate article:

For Contour & Mystique, see A/C-HEATER SYSTEMS .

For Windstar, see A/C-HEATER SYSTEMS .