I have a 2004. 5 Dodge 2500 SB. I have changed the oil every 3,500 miles. Everytime I change the oil I notice the coolant level has dropped. I now have 19,300 miles on it and the coolant tank level is below the add mark. I have never added any coolant. I am new to this site and I have reviewed some past threads but am still unsure if this is normal consumption for a Diesel or not. I have looked it over very carefully and find no external leaks on the engine.