Losing coolant from coolant system

[SmartBrabusDerby]

Hi, hopefully someone can help. My Smart Brabus FourTwo 2011 is losing coolant. I have pressurised the system and no leaks found.

The oil isn’t watery but there is a little water coming escaping out of the exhaust.

Initial worry is that it’s the head gasket. Car has only done 26k so hoping not. Anyone else had a similar issue?

Cheers