Did you drain from the block or the radiator or both? If it was from the block, maybe the coolant picked up some oil/sludge from the outside of the engine while draining? I couldn't tell without seeing what the coolant looks like.

__________________
2001 Dodge Ram 2500 Cummins Turbo Diesel - 4x4, auto, 3.54 gears, long bed
-------------------------------------
'92 300D 2.5 Turbodiesel - sold
'83 300D Turbodiesel - 4 speed manual/2.88 diff - sold
'87 300D Turbodiesel - sold
'82 300D Turbodiesel - sold