Does anybody know what those white dried-up drops are? I checked out another Boeing 737-800 on the ramp and it also had the same defect so I'm guessing this is a common issue, or is it? This shows up the outboard side of the exhaust by the way.
Just a guess, but it looks like deicing fluid that dripped onto the hot exhaust cone just after the engine was shut down. The origin of the drops suggests something running off the pylon side panels directly above, and the vertical tracks show that the engine was off, but the cone was still hot enough to bake off the fluid, leaving the runs of glycol residue.