Last month I purchased a 2009 Dodge 2500 HD Cummins 6.7. The previous owner said it had a sinister egr delete and tuner. Everything good till this morning while out driving started to lose heat from heater fearing head gasket I opened hood and smelled and saw wet coolant from P.S. I checked radiator no. Coolant, checked oil and it had no signs of coolant. Truck did not overheat highest temp was 200 f. I added few gallons coolant, truck started no issues, heat was back on oil pressure and temps good, however I saw at the coolant riser tube where the coolant bleed screw is, the tube is wide open about one inch past bleed screw, no hose attached, no plug blocking it off just wide open metal pipe, I believe it has been this way since I purchased it but have never had the leak, any reason to have cut the riser pipe? What would cause it to leak all of a sudden? Also all coolant lines appear to have been re routed. Any help would be appreciated as I'm new to diesels thanks.