Cummins ISX 500

Hi guys, i have a 2006 KW with Cummins ISX. Recently I seem to have a coolant loss issue.
The Coolant was low and could not find any leaks on outside anywhere. Topped up Coolant and ran the Truck for a few days. When working it hard it blew coolant out of Radiator overflow port. Then low coolant warning comming on!
Thought it was the cap so we replaced it. Also replaced coolant sensor.
You can smell coolant when the fan kicks and also see some spray against hood. ( the overflow drip line is missing).
Any help appreciated cant seem to put a finger on this one.
History of Truck is Head Gasket 3 years ago. Egr Cooler , EGR and Turbo 2 years old!
Seems to pull good and runs smooth! Just tried another new cap 15psi, still same!
The resorvoir is not empty just makes it low enough to trigger light! Thanks.

 

Ok, gonna have cooler tested