Originally Posted by bdcardinal
The secondary system is for the EGR cooler, Charge Air Cooler (intercooler in normal speak), and the transmission cooler. Not as critical, but still worth changing,
Generally the system is drained and filled assuming there is no contamination. Contamination would be anything not coolant in the coolant. On the 6.0 diesel this could include casting sand which was why the coolant filters are such a popular add on part.
When you say drained, does than mean they drain the radiator, block, heater core, etc? Then refill?