Some 2011 Ford F-150 and 2011-2012 Mustang vehicles (excluding Boss) built on or before 3-31-2011 and equipped with the 5.0L engine may exhibit an intermittent metallic rattle or scratching type noise in the area at the front of the left hand cylinder at idle with the engine at operating temperature. This noise is not a typical upper engine tick or tapping noise.
With the vehicle in Park, start the engine and operate at idle, allowing the engine to warm to normal operating temperature.
Using a mechanic’s stethoscope or EngineEAR, evaluate the area at the left front cylinder head for metallic or scratching type noise.
If this noise is detected, replace the left hand primary tensioner and the left hand timing chain tensioner arm using kit P/N BR3Z-6L266-AA. Refer to workshop manual section 303-01C (camshaft-left hand removal and installation).
NOTE: Failure to replace both the primary tensioner and timing chain tensioner arm may result in overloading of the timing chain, and under certain conditions could lead to timing chain failure.