Diesel Noise Not a Concern
Some 2008-2010 Ford F-Super Duty 250-350 vehicles equipped with the 6.4L diesel engine may exhibit a random engine ticking/tapping noise that is most noticeable when engine coolant temperature is 185 degrees Fahrenheit or higher and from base idle to about 1,500 rpm.
Some customers complain that this noise becomes more evident after 3,500-5,000 miles after an engine oil change.
The ticking/tapping noise is most noticeable at the rear of the driver side front wheel well.
All 6.4L Powerstroke diesel engines exhibit this normal noise. The noise is caused by the relationship between the engine bock, crankshaft journals, bearing inserts and oil viscosity.
This relationship allows a pulsation that resonates through the cylinder block and is heard as a metallic ticking noise. According to Ford, this condition is present on all diesel engines.