octavia EGR Valve Cooler 04L131512D

Been advised my coolant leak [4 months of 10mm per week loss] is an egr coolant. Anyone with experience of this?

Have a round-trip of 400 miles over the weekend to make I cant miss.

Have been told its going out thru exhaust [not sure if thats correct, think its a guess to be honest as tried everything else apparently]

Damage caused if any, other than topping up 10 mm every 200 miles.

Thanks for any info.