Some 2013-2018 F-150 and 2017-2018 Expedition/Navigator vehicles may exhibit an intermittent grinding noise coming from the right or left IWE area in 2WD mode. This may be caused by an intermittent leak in the check valve. Before completing any normal diagnosis suspect that the check valve is the root cause of the issue. If the check valve has been ruled out as the root cause for the issue refer to Work Shop Manual 308-07 and follow normal diagnosis.
