Search for external leaks 1st, g13 coolant will leave white deposit marks when it dry.
In my car, after replacing the thermostat as the rubber hoses has to be removed to do this, when mounting all in place one nut that attach the hose to the oil filter housing as giving support so that the hoses and the engine move together, this nut got loose and felt. This has the impact that the engine moves but the hoses don't quite follow the engine movement so it stretch the hose on hard acceleration and provoques temporary leaks on hose connections. After putting the nut again this leak stopped.
If you don't find any external leak, my bet will the the egr cooler/radiator leaking internally (coolant is used to cool down exhausted gases before introducing them in the intake). This coolant leak heads to the intake, and as is internally you don't see it without taking it apart for inspection.
And EGR coolers are very prone to fail.