I have 2008 F 350 Turbo diesel, it makes a loud humming noise that seems to be coming from the left side of the motor. Some times it's very loud and pulsing ( almost seems to be harmonic). Any ideas before I call the dealer?

 

Only idea I have is to check your power steer fluid. Ensure all your fluids are in the right range.

fuel cooler...be sure to check that.

 

Scott is likely correct, it sounds like your fuel cooler is low. This uses an electric pump to circulate the coolant, and this pump makes a loud noise when it runs out of fluid!