DS3 diesel coolant leak

[davetheds3dude]

Hi I bought myself a 2015 ds3 1.6 diesel and I'm loosing coolant. I'm currently on R plates and doing a 40 miles commute every day and the coolant is dropping after every 3-4 weeks. It is dropping way down pass min. My dad had the car for a week and was doing 80 miles a day a lot of motorway driving and the reservoir was at min at the end of the week.I took the car back to the dealer and they pressurized the system and said there was no leaks and to bring it back when the reservoir is low again. Is it normal to have to top up the coolant reservoirs on these cars regularly Ive never had a diesel before it doesnt seem normal to me. Ive check the oil, it looks fine and no white smoke out the back. Any advice would be appreciated
Thanks David

[Chris_Blue]

No. Its not normal to use coolant. Ive got an edhi 110 and dont loose any
Is it coming out the overflow tube by the LHS of the radiator?

Look under the oil filler cap and is there any sludge there?

[davetheds3dude]

Ill check the overflow tube, the oil cap is clean