[Pix2]

Hello there,

I am novice to this Forum. I was reading all over the topics but couldn't find a relevant to my issue.
My hope is that some expert can answer my question:

I have a 2010 F07 535i GT.
My engine code is N55B30A
The current millage is 140 000 km.

The issue is that the coolant fluid is vanishing from the system but there is no sign of leaking.
I need to top up from min to max at least every 100 km in city. If going to highway then after 25 km the BC notice me to stop and top up.

This whole issues started with change of the cooler radiator which had a leak.
Then I had to change 6 months later the water pump at 130 000 km which went down.

Since these changes I still have this issue which is almost a year know.

I was several times in different workshops where the system was checked for high pressure but we could not find any sign of leaking in the system.

The oil is dark brown as usual. The engine works fine I do not feel any difference.

Where do I need to look, how can I find the leak? Is there any known issue among the F07 users with similar issue?
Please, help!

Is there any method to find out if there is more O2 in the exhaust which indicates that the coolant is disappearing there?

Regards
Pix