I'd suggest calling Freightliner with your VIN and ask if your chassis had the coolant filter installed.
In the meantime, you can look on the driver's side of the engine, above the oil filter and toward the rear of the engine (closer to the transmission) to see if there is a filter. I believe that's the general location, but not sure on an ISB, or if an ISB even has a filter.
Larry, Eileen, and Finley
2004 Alpine 36FDDS
Third motor home, first Alpine, no need for another.